I've done a bit research into this, but not brought myself to build anything, as I can't decide between vibrate or tumble!

The most common commercial tumblers I found were essentially plastic lined square boxes with a couple bearings and a motor. On the homebrew front, the most popular method seemed to involve a plastic barrel in a mounting frame running on a couple bearings (just need to fit a new barrel when it wears out, whereas the commercial units have to be relined). Spin it end over end and you shouldn't need any baffles. Plastic is preferred as it helps reduce sound, and is far less likely to damage softer parts.

I'd love to speak to someone who's got experience with finishing methods, as I never found any real answers to what method works better for what. I know a lot will be down to media choice, and how quickly you want to acheive the desired result, however it would be good to find an independant opinion that isn't biased into selling me something!