I once made me a small polishing contraption from an old printer, quick and dirty. I used the powersupply from an old mobile.
These jamjars with 6 corners do work well for small pieces. I used this to create a uniform surface before applying pimer and paint.
As the polishing granulate I've tried: cat litter, steel chips, pieces of quartz etc and a granulate from walnut shells.
One has to find the proper conditions by trial and error. Polishing time can be up to 24 h.