You might want to check Carie Nelson's video on Youtube.
She gives some great tips on filling and stuffing for pincushions.
I've only made one and I used sand in it for weight. Not a big fan
of sand. I prefer wool. Have a few of those in my sewing room.
I think the lanolin in wool keeps the pins lubricated. Not sure.
Anyway, I keep all my pins in those wool pincushions.
Here's the video.
https://www.youtube.com/watch?v=-TfvvPx_ydw