I recently bought at barely used Taurus PT111 G2 compact 9mm pistol, which had some minute flecks of rust starting where it had set up without cleaning, on the spots where the fingers had pushed the slide, the safety and the slide release.
I decided to try NEVR-DULL polishing cloth, which is a roll of cotton sheeting in a can, with some oil and other stuff in it. You just pull out a bit from the center and rub away tarnish. It is really super on stainless steel, nickel and brass, like the small buckles on equestrian tack and dog leashes.
Ever where rust could not be seen, this stuff rubbed some off and onto the cloth. Then I cleaned the pistol as normal. It looks great! No bluing rubbed off, non of the matte finish polished. I wish I had taken a "before" photo. A can of this stuff would last most people ten years.