Crushed walnut shells (sold as lizard litter at the pet store) proved to be a much better filler for pincushions. They add a bit of heft which keeps the cushion from lifting up with the pin you are trying to extract. Maybe the coarse grains also sharpen the pins? Who really cares about that? They are fun little projects and making half a dozen or so might seem excessive until one looks on Flickr for the real zealots.