I've used nearly everything imaginable in my tumblers over the years from beach sandt to dried beans, rice, wood chips, BBQ charcoal, cat litter to commercial de-burring media, ad infinatum (sometimes uncontrolled tinkerer). For an additive, Nu-Finish is popular, and I've found almost any auto cleaner/wax works, and now I've been using Turtle Wax cleaner polish ('cause that's what I've had on hand for a while). After all the experimenting, I've settled on corn cob blast media, 14-20, with an occasional dollop of mineral spirits or auto cleaner/wax. This works for me and my tumblers; rotary and wobbler...