For Brushed SS use a very light 3M Final Stripping Pad with oil, work with the grain and work slow. This method takes practice but will make SS pistols look new again.It only works on brushed SS. Don't use it on polished SS
Start out on some scrap stainless if you have some or a part of your pistol that does not show and work slowly and very lightly.For SS that has been polished I would recommend mothers polishing cream, also a lead Crocus cleaning cloth.
Tony