Hmmmm..., never thought it could get so complex or expensive. I have a big Lortone rubber-drum tumbler for the big stuff, and a little Thumbler's Tumbler for small lots of pistol like 44-40 & 455 Webley.
I just use cheap bulk long-grain rice (0.29/lb) and a big blop** of Meguiar's polishing compound from the local car-parts store. Turn the tumbler on in the garage at bedtime, next morning they look like new.
When the rice gets too black, I just throw it away and pour in some new. Guess I'm not having nearly as much fun.....
**Blop: highly technical measurement. Note that metric blops are smaller than American.