Hey Don, I use plain colored aquarium gravel with dish washing liquid and a splash of ammonia. Heed Jeff's warning.....don't mix copper and clad, the clad takes on the copper color. I have a single barrel Harbor Freight tumbler and I usually let it run from 2 to 4 hours depending on the amount of coins I throw in. Some guys say they change the water half way through but I just let it run and dump it at the end.
Good luck!!
Dave