Lol this reminds me of a place that sprayed armor all on the rails of the 2 gold crowns. Boy it made those rails look good. But the overspray on the cloth got on the balls thence my tip. It expanded like something from a chemistry demonstration.if i read this right then friction from coins improved the tips? you might as well put them in a vibratory tumbler to speed up the process in that case. maybe add some grease.