The foam ear plugs that come in jars work very well for this. Cutting all those corks seems as if it would be a time consuming chore, and the ear plugs are bright colors that would be easier to notice on a quilt. I've tried them on a small quilt and loved the way they worked. Not a single pin fell out, yet they were very easy to put on and to remove. I probably won't get around to using them on everything until my supply of spray baste runs out.
Thanks for contributing the hint. If it was the middle of the night and I ran out of the ear plugs, I could dig around here for a bag of corks that have accumulated over the years. We knew they'd be useful for something eventually.