I’ve done some testing with ceramic media in a vibratory tumbler, it tends to make the outer surface white so I sometimes use wax to restore the original color. I’ve mostly found it useful for removing the glossy finish in the plastics, and less for removing layer lines. I need to do some more experiments though, maybe with something more abrasive.
There’s some pictures at http://www.whirlinglight.com/vibratory-tumbler-ceramic/. There’s also some other posts there about metal coating with screws.
I’ve also tried an air eraser (mini sandblasting pen) but didn’t find it very useful. It mostly made the plastic whiter in a very small area.