My wife had a bag of foam wedges that she uses with her cosmetics that works fine. Afterwards, I recall seeing foam stuck in Bigsby tailpieces over the years. Now I know that it may not have been to kill a buzz.

All you have to do is just make a curve in the string right at the ball end. You can do it with your fingers if you on a gig or with a small set of needle nose pliers if you at a bench. Make sure the curve is done with the hole in the ball end facing up. Then just thread the string over the top of the roller and "hook" the ball end onto the string post. Keep a little tension on the string as you thread it through your machine heads.