My strong recommendation is to forget it. There are all kinds of cold blues that supposedly work magic but I have not found one yet that is durable; most wear off in a few days or even a few hours depending on the handling and use.
In addition, any attempt to just "touch up" the worn areas will very likely look a lot worse than the current wear. To have it hot tank reblued will not be much better, as the wear will only recur and the polishing necessary for rebluing can really hurt the looks of the gun.
There are some coating type finishes that can be done at home, basically laquers or epoxy finishes. Some require sanding the gun, others can go on over the original finish.
I know it is a personal opinion, but I would rather see a gun with honest wear than one covered with a spray finish.
Jim