For grunt cleaning, crushed walnut works the best. Often times, I find that walnut, combined with Berry's brass polish (or MidwayUSA's White Lightning) does an excellent job of cleaning and polishing, although if I want the absolute brightest finish, I would use a final stage of corncob tumbling.
In a pinch, short grain rice works surprisingly well. Having come from a Korean family, I know it sounds sacreligious, but I've always been in the habit of buying rice in the 50 lb bags, so using it for such a purpose didn't put too much of a dent in my grocery budget. I suppose that my use of uncooked rice in mesh bags as a cheap dessicant would also qualify for such sacrelige!
If you choose to try rice, there are a few important details to which you must pay attention:
1) Short grain rice works much better than long grain rice.
2) Don't use the abomination known as "Instant" rice, or any rice that has already been pre-cooked in any way, shape, or form. This is too soft and too weak to work properly.