I have recently use Blue Wonder and 0000 steel wool. No harm to the finish and good results. I had run out of bronze wool, but the steel wool worked fine. All of the other suggestions will work fine as well on surface rust.
I had a little rust forming on the hammer of one of my revolvers and at the time I had started using a different brand solvent called Montana Xtreme. I decided when cleaning it that day to put a dab of their stuff on the rust spot and I have to say, this solvent is one of the most powerful, strongest smelling, craziest knock you out solvents I have ever used. I rubbed it in and rust was gone. Try them but make sure you've got some sort of mask on because the smell will knock you out. They claim it's not ammonia or acid based, but wow... Products « Montana X-Treme