Definitely just an oxalic acid bath alone first. I know people swear by using steel wool but here are my thoughts on that:

Steel wool is going to produce small scratches in the chrome. Over time, if you aren't waxing or polishing with regularity those scratches are going to become points for more rust to start eating at the steel underneath. Especially if the bike is going to be exposed to the elements.

I can almost guarantee that the OA bath alone will fix your problem. A quick polishing with a chrome polish of your choice should leave them looking almost like new. Should you have significant pitting a good coat of wax should help keep those points from becoming rust magnets. From the looks of those fenders in the picture they won't have much trouble with that.