tumblers and media

[mrmiskin]

couple of questions firstly tumbling cases, should all cases be tumbled before reloading? what does this do that just wiping down with a cleaner wont? what is the best tumbler out there on the market. i have read that there is some media that causes the cases to wear i believe that it has mica in it. i have seen some that is just crushed walnut hulls. i just reload for the family and i am not into it on a large scale. thanks.