I have this done for me at the moment and am looking to build my own equipment.
Mine is done to increase resistance to sea water and as far as I know vibrating with stainless balls is the quickest and best.
But filling a tub with stainless balls is expensive... And I have yet to locate a source.
It takes the company that does it 20 minutes to get it done. Up close you see that the surface is dented.
If you want a high shine, electrolytic polishing may be better.