There's a fascinating product called 'Buffalo Bore' (not the ammo). It's like a big Brillo pad, but the individual strands are wide, thin, and flat, like little knife blades. It has allowed me to remove surface rust without changing the underlying finish at all. Just takes the (proud) oxidized metal and leaves whatever blue is underneath without scratching or removing the finish. Don't know how they do it, but I experimented on loser guns and pressing hard didn't leave any scratches. Weird, but cool.