I have not tried this but it sounds reasonable. A friend of mine at a local shoot mentioned that when his brass is extremely dirty, such as stuck on mud or sand, he uses rice in his tumbler. Cheap enough to use more than once. I thought it was worth passing on to all the reloaders on the forum. Anyone ever use this method?
I believe the whole idea of using rice was not to polish but rather to knock off all the mud and debris. I know where we shoot at Saltillo the mud is very hard to remove from brass if it is the very least moist.