I use both, together. I use a 50/50 mix of the fine walnut bedding and the fine corn cob bedding, both of which can be found at you local Petco (or similar pet store). The walnut is usually found by the bird stuff and the corncob is usually either in the same place or by the small animal stuff. The media that you can get at the pet store is MUCH cheaper than the same product at your shooting supply store, and works just as well. After mixing it in another container (I use an empty cat little jug to mix and store the media), I put an appropriate amount in my tumbler and add a couple tablespoons of Iosso Brass Polish and let the tumbler run empty for 30-60 minutes to mix and dry the polish with the media.

I started out using the Lyman green treated corncob media, but found that that stuff took up to 24 hours of tumbling to fully clean and polish even moderately dirty cases, and it is very expensive. The life expectancy was also very short. After three or four tumbling sessions it's be black as coal and would not longer polish the brass to my satisfaction. The 50/50 walnut/corncob media I use lasts through at least 10 cleaning sessions, costs half as much, and polished twice as fast. If I am tumbling fired cases that never hit the ground, they can be clean and polished to a very bright shine in less than 3-4 hours. Dirtier cases require at most 6 hours to be sparkling clean and shinier than new.

Mike