You need a tumbler and abrasive media, a lot of makers also do a pre-treatment such as bead blasting or an acid wash to help create contrast in the finish.
The tumblers come in 2 types, vibratory or rotary. The vibratory ones work in the same manner as a reloading tumbler, the rotary ones are fairly self-explanatory and resemble a stone polisher, or a small cement mixer. The media comes in many different types, shapes, weights and sizes, and needs to be selected for the application. This part can get pretty involved and is worth some research.
You generally need to have a fine finish before you start tumbling, otherwise it will tend to highlight flaws and imperfections.