For vises: Most of the time I use a 2.5" ScotchBrite disk attached to a mandrel, powered by a high speed air grinder.
For pocket knives: Sometimes I use Semi-Chrome and a buffing stick, or diamond grit mold polish.
During my working life, doing some mold repair: I've used >600 grit sand paper and polishing stones.
I also have my radial arm saw set up with a 10" buffing wheel & a 2.5" Scotchbrite pad to polish small metal details.
Hope this helps