I know... I know... you've made the top for your pincushion. Now what?
I'll get to some non-pinnie pattern next week but in the meantime, I did promise to get to stuffing, filling and figuring out which is the best.
That's easy. What sort of pincushion are you making?

The first, last and most important thing to know here is that there isn't really a right answer. At least I don't think there is. How the finished pincushion is going to look and feel is very much a matter of personal preference. While there are some things that will work best if you do things a specific way, even that has a degree of "what you like best".
So the first thing to decide is this - do you want a light-weight pincushion or one with some weight and substance to it? Or does that not matter to you? Do you like a pincushion that is soft, or do you prefer a firm, relatively solid pincushion. And what is the shape of your pincushion? And is this pincushion something you actually intend to use, or is this something pretty that will sit on a shelf in your sewing room? Your answer to each question will then factor into which filling you use and how much you use.
Personally, I prefer a firm pincushion with some weight to it. I admit it - I tend to be pulling or replacing pins without really paying attention. I'm reaching in the general direction of where I think I last saw my pincushion without really looking at it to see what I'm doing. So a pincushion that isn't going to slide around while I try to remove/insert the pin is a must. With few exceptions, I want to be able to actually use my pincushions. That doesn't mean that I actually do use them, I just want to know that I can.
So let me go through some of the options for stuffing - filling.
Stuffing / Fiberfill / Wadding. This comes in cotton, polyester, and bamboo. Wool roving, stuffing or batting bits can also be used though I don't see that done very often. The benefits of the stuffing is that it can be stuffed into a point and it will hold that shape. For any shaped pincushion, this kind of stuffing is the best to use.
My preferred stuffing is cotton stuffing - Sweet Dreams Cotton Stuffing. I like the others and I've used them, but the cotton stuffing is my favorite because of the weight, feel and density of it. I can move it around easily within the pincushion using my knitting needle or stuffing fork, and it will compact down fairly tightly. I sometimes find the polyester and bamboo fiberfill a little springy - they bounce back at me - and I don't really like the silkiness of the fibers. (That's simply a personal preference issue.) I also prefer the feel of the cotton stuffing - it can be firm without being hard, soft without being springy.
With very few exceptions, every single pincushion I make uses some amount of cotton stuffing.

For this watermelon pincushion, the cotton stuffing is used to stuff the two ends, and then to fill in along the sides. After I stuffed the points, I filled the pincushion with crushed walnut shells as much as possible, then filled in the spaces and gaps with stuffing. The crushed walnut shells will keep settling so keeping a smooth edge and a fully-filled shape - especially along the seams - can be a challenge. The final proportion of cotton stuffing to crushed walnut shells for these pincushions is about 50/50.

This tetrahedron-shaped pincushion was filled/stuffed in much the same way. There is cotton stuffing in the points and the rest is filled with crushed walnut shells.
Whenever I use a combination of the two fillings, I like using the cotton stuffing to cover the loose shells while I'm trying to stitch the opening closed. It is also a very good way to keep a tight, firm filling by adding little bits of stuffing as the opening is stitched closed - the stuffing is pushed in under the seam as it is being stitched closed.
That is especially the case with round pincushions. I think the biggest challenge with round pincushions is keeping them round. Using the stuffing fork or knitting needle to place stuffing/fiberfill along the edges is a huge help in stuffing round pincushions.

Sand - Silica or Play Sand. Sand is a very popular fill for pincushions - it gives a nice weight to the finished pincushion, it is easily found and not very expensive. You can find both kinds of sand at hardware stores and home improvement stores like Home Depot. The one caveat to consider is that in recent years, there has been a fair amount of literature warning against potential health hazards from both silica sand and play sand - from toxicity to respiratory issues that can arise from inhaling the fine dust that is part of the sand.
I don't use sand for the simple reason that I generally prefer the results I get from crushed walnut shells. And I emphasize - the I get. Other people have made pincushions that I consider "perfect" using sand - the issue is that I don't get those same results. I find that in short order, the sand compacts down in a way that makes the pincushion a little softer and floppier than desired. For me. Only me.
Crushed Walnut Shells. This is what works best for me. It's available from the pet store - e.g., PetsMart and Petco - and it is generally found in the bird or reptile section. It is sold as cage litter for birds and lizards, and a 7 lb. bag usually costs about $10.00. A bag that size is enough for a whole lot of pincushions. Twenty? Probably. I think I need to start keeping track.

This is the jar I keep in my workroom. (The patchwork cow was a lovely gift. She keeps me company. She's got pink horns and hooves, of course she's a girl!)

This is what it looks like - it looks a bit like coarsely ground coffee. I use the 1/2 cup measure to scoop the shells into the funnel - that is to get the shells into the opening of the pincushion. A small baking sheet with sides - something like a quarter-sheet or jelly roll pan - is a terrific tray for filling. Anything that falls out - and trust me, some will always fall out - is caught in the tray and easily put back in the jar.
Because I like a firm pincushion, I fill and squash... fill and squash... until I've made a huge mess after spilling crushed walnut shells everywhere. I'm kidding - mostly. I have done that. The point is that to get a really good firm fill, I do "pack" the shells a bit.
I also fill the pincushion to the point that it's almost too full to stitch closed. At that point, I hold it closed as best as possible and "test" the firmness. It is going to "relax" down a tiny bit so having it a tiny bit too firm isn't a bad thing. If you've used a felted wool backing for the pincushion, it will probably "relax" a little bit more. Adding a little cotton stuffing as the opening is stitched closed will help keep the pincushion really firm - if that's what you prefer.
The most important thing to remember here is that some will be a little more firm than you want them and some will be a little less firm. Getting more consistent results will come with practice - you'll know how firm it needs to be before stitching it closed to get it to finish the way you want. The really good news is that whatever you do isn't permanent - you can always un-do the stitches to open the pincushion to add or remove some of the fill. Been there, done that! Several times.
Lavender. If you - or the recipient of the lovely gift you're making - loves lavender, adding a little bit to the fill is a terrific was to make a really unique pincushion. I love the smell of lavender and one of my favorite pincushions has a little bit of lavender mixed into the crushed walnut shells. The scent is very subtle - I didn't use much and the scent does dissipate a bit. Dried lavender like this is fairly easy to find and not overly expensive so if you really love it, it really is a nice addition.

For the pincushions I've made with lavender, I used about a 1:2 ration of lavender to shells - a generous 1/2 cup of lavender to 1 heaping cup of crushed walnut shells. I mixed them in a bowl until the two were well-blended, then I filled the pincushion until I reached the desired firmness.
Sawdust. This isn't something new, most vintage pincushions are filled with sawdust. If you know any woodworkers or carpenters, then you've probably got an easy source for sawdust. If you don't have that kind of source, you should try your local lumber yard or Home Depot. Dress nicely, fix your hair, put on some make-up and bring a bag, box or bin with you.
It's like this, my local Home Depot said "no", citing all sorts of potential problems and liabilities while the Home Depot across town happily filled two bags for a friend. A pretty, petite, blonde friend. Rather that drive across town to get her to get my bins filled, I called a local woodworking shop. They were wonderful - they generously filled fill two shoe-box size bins for me. But they did warn me that some exotic woods contain oils and chemicals that can be poisonous to small children and animals. (On a side note, calling a woodworking shop to ask if they have sawdust will go down as one of the funnier telephone conversations I've ever had.)
This sawdust comes from a friend's husband - he likes to build things.

Those pieces that look a little big really aren't - they're lightweight, fluffy and quite soft. And truthfully, they look a little bigger in the picture than they do in real life.
The first challenge that comes with stuffing a pincushion with sawdust is actually getting the sawdust into the pincushion. A regular funnel doesn't really work because the hole is too small and the light, fluffy sawdust just sits in the top of the funnel unless you push it down and through... which is made difficult by the small hole of a regular funnel. I used a make-shift funnel I fashioned from a sheet of template plastic held together with tape. I was able to scoop the sawdust into the top of the make-shift funnel and push it through the bigger opening. The second challenge is that the light, fluffy sawdust has to be smooshed down to "pack" it in. So the process is stuff and smoosh... stuff and smoosh... stuff and smoosh... stuff and smoosh... a lot. It's time consuming and there came a point where I was sure it wasn't going to work.
I also found that the shape was a little odd until it was firm and full. That's when I found out that I could manipulate the shape relatively easily to make it square, firm and flat.
But the time and the extra work is definitely worth it.

This is a pincushion I bought a few years ago from Stacy Nash, the gloriously talented primitive cross-stitcher.
If you have a chance to use sawdust, I highly recommend it because the look and feel of the finished pincushion is unique. Sawdust gives the pincushion a firmness and feel that is hard to describe - it is almost like it were a solid piece of dense foam or cork. Except that it isn't hard. While it isn't nearly as heavy as it would be filled with crushed walnut shells, it still has a very nice weight to it.

This is the first pincushion I made with a sawdust filling. After hearing from Stacy how she filled her pincushions, I was anxious to try the method so I cut down a needlepoint pillow that I knew I would never finish to make a pincushion. I've since made three more pincushions with sawdust stuffing and I am a fan.
Emery. While I don't use emery, it is a popular enough option that I feel it important to mention. Emery is a fine sand made from grinding a very hard rock. The sand is used as an abrasive material suitable for a variety of purposes - nail files, cleaning machinery,, etc. While it can often be found fairly easily in large quantities, smaller quantities are available on eBay and Etsy as "pincushion supplies". Depending on where you find it and who you purchase it from, it can sometimes be expensive. The problem with emery is that it is not without some controversy among sewists and pincushion makers.
Emery has been around a long time. Your first experience with it is probably the same as mine - it is what was used to fill the little strawberry that dangled from the large tomato pincushion. The strawberry was filled with emery, the tomato was not. And therein lies some of the problem. Emery is promoted as a desirable pincushion fill because it sharpens the pins and needles. The problem is that the pins and needles shouldn't be left to sit in the emery as it "can" corrode the plating, leaving a rough surface that can pull and snag the fabric.
Over the years, I have seen testimonials from people who claim to have used emery for years and year without every having a problem. And I have seen equally convincing testimonials from people who have had all sorts of problems with corrosion, including snags, tears and ruined projects. I have no doubt that the stories and experiences of both are true, and that there are many factors that probably affect whether or not I will have a problem with emery.As such, I have chosen not to use it. Not because I believe it could be a problem but because there are so many easily available, more affordable stuffings that give me the results I am looking for.
Everything else. There are a few more stuffings that I've heard in my travels and research. Rice. Plastic pellets. Fabric scraps. Batting scraps. Hair - like the kind you find in your brush. I'll say it for you - ICK.
At this point, you know which stuffings I like and why.
But there is one last thing to mention, it's about how much to stuff the pincushion. Even if you like a firm pincushion, there are times when you want to leave a little bit of "squish" room.

If - when - I make another pincushion like this one, I won't fill it quite as firmly before closing it. I'll leave it a little softer and squishier. The more firm the pincushion, the less indentation there is when the perle cotton is cinched for sectioning. The sections do show - and they show more in person than in this picture - they would show even more if I hadn't filled the pincushion quite as firmly. Live and learn, right?
That's really the point of all this - the more pincushions you make, the easier it is to know how firm to make it to suit you. Knowing which pincushions to make firm and which ones to make a little softer comes with practice and experience - and it isn't so much that you'll get better as you'll figure out what you like and how to get it to look that way. The good news is that even if you have made the most incredibly special pincushion ever - E.V.E.R. - but then not been happy with how it was stuffed, you can re-do it. Carefully remove the stitches closing the pincushion, empty the stuffing and start over. It isn't like you've painted your great-grandmother's family heirloom dining room table orange. You can have a do-over.
And/or you can make another one.
I will babble on about pincushions one more time - a little bit about the whole sectioning thing and round pincushions.
That's it for today though.
Thank you very much for the birthday wishes - I appreciate it. I had a very nice day - I didn't have to cook and I bought a Tiramisu Cake to celebrate. (I couldn't decide what kind I wanted and I didn't want to bake one.)
Have a happy weekend!