I've been using the large white Dunlop thumb picks for forever now. I place them in boiling water for a few seconds, immediately put it on my thumb and dip thumb into cold water or place it under a running spigot and I have a pick that sits comfortably and securely on my thumb. (be sure not to leave in hot water for more than a few seconds or it will lose it's shape entirely). I then shorten it a bit, following the contour of the blade, blunt the point a little and bevel the underside.