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Introduction To Buffing and Polishing - Caswell Inc.
There is a chart halfway down with the rouge color corresponding to the metal. Green rouge is designed for polishing stainless steel. Red rouge is mostly used for silver and gold. Tripoli is a rougher rouge that is used before the final ones.
You must decide what sort of finish you want (or already have). They can be various types of "brushed" where there are thousands of parallel scratches or some sort of high polish like a mirror.
All of the damaged scratches need to be removed and then the polish gradually brought up with finer and finer abrasives. You have 3 options for abrasives: sandpaper (for metal finishing grit 400 to 4000 is mostly used), 3m polishing pads (mentioned above, they have the same grit as sandpaper embedded in a pad), and rouges (they have the grit in wax that you apply with a soft cloth or buffing wheel). Steel wool is tough to control so I prefer not to use it.
Lightly scratched metal might be as simple as a light sanding with 2000 grit sandpaper then a little rubbing with green rouge on clean cotton towel.
Badly scathed metal might take heavy sanding with 400 grit paper (be sure to keep sanding even ) and then a progressive light sanding of 400, 800, 1200, 2000, and then polish with green rouge.
Always thoroughly clean all surfaces between changing grits. Use a piece of cloths or buffing wheel for ONE grit only. You can use metal finishing sandpaper wet (water or oil) and the metal that is removed will not clog the paper.
Practice on scrap to become proficient before fooling around with anything valuable. You need to learn what the various finishes look like and how to match them.