Since started powder coating by tumbling I always seemed to have a problem with boolits hitting each other and leaving marks on each other or the powder would over coat on some and not enough on others, I would have to try and knock it off when putting them on a tray for baking, this afternoon I was thinking about this and I don't know if this has already been done but I have never seen it yet, first I took some of my boys air-soft bbs that are plastic and poured enough to cover the 50 boolits I had in the plastic tub than put 2 table spoons of powder on every thing and started tumbling for 3 min. after 3 min. I checked the boolits and found them perfectly covered no marks from banging into each other and no over covering with powder, The plastic bbs were totally covered themselves and provided a medium for the boolits to tumble in, it worked so good I tumbled 500 this afternoon with no problems I usually have with lack of coverage or over coverage. try it you might like it, one thing the amount of air-soft bbs you use depends on the amount of boolits you use, if you don't use enough bbs your boolits will mark each other up when they hit each other and if you use to much you will have to dig through everything trying to find the boolits. I am not saying this is cure all, but it works for me and thought I would share it.