I use an Ikohe model K149-160 magnetic tumbler. You can adjust the speed, the time between reversing and the total time.
It's great for getting your pieces shiny down in most of the nooks and crannies. You still need to refinish it first, down to an emery or rubber wheel finish. After tumbling you're left with a very fine orange peel finish, tiny little dings from the pins, but it is shiny. Silver is softer than gold so with that the crisp edges are more dinged up and a bit rounded after use. You still need to polish it to get a mirror finish.
The real benefit is shining up those hard to reach areas. Id recommend Gessweins powdered soap #852-1039, it works well. I've tried liquid soaps and I got more thick black residue with the liquid than I do with the powder.