I guess I'm lucky, I've never had a rust problem, with any of my guns or gear. On external blued metal surfaces, I apply a generous coating of car wax, something I learned to do in the police academy 40+ years ago. All of my arms are secured in climate controlled safes, in a climate controlled house. I even use a silicone cloth to wipe down my stainless stuff. My home is in the Pacific Northwest, which has been known to be damp.
In the meantime, as things have progressed, I go stainless, parkerized or polymer when I can. Among my collection of Mini-14 (and AR) magazines, I have waxed steel, stainless and polymer magazines. Same deal with pistol mags.