I had an issues with my Knight ML a few years go after a hunt in the rain and I didn't dry it off when I got home. Needless to say it was pretty rusted that it wouldn't wipe off.
I went to Wal Mart and bought a rebluing kit made by Outers and in a short afternoon after following the directions reblued the gun and it has been perfect ever since (probably 8 years now). Not even a hint of rust or fading. Unfortunately I think the rebluing may have been better than the first.
I really dont like steel wool because it breaks apart and then rusts. if it is just a couple spots, spray it down with rem oil, and wipe clean and then go after the small rust spots with a penny. and re-oil.
Pick up a bottle of "Rusteprufe Nitro Slovent & Rust Prventing Oil".
The applicator looks like a small chamois and comes in a short round jar, extra oil comes in regular small bottle. Absolutely amazing stuff, wipes the rust right away.(I'm talking about surface rust - if you have deep pitting, I don't know how it would work). It's made in Wisconsin since 1938. I got mine at Miller's Gun Shop in New Castle, Delaware.