Usually Brownell’s Oxpho-blue; the cream version of that seems to be easy to work with. Also, I have a buddy who does gunsmithing work and has a hot-bluing setup. Sometimes I bead-blast the steel parts and drop them off with him; he dunks them along with whatever paying job he is working on. I keep him supplied with .32 Long Colt reloads for his old Marlin.
Thanks. I need something that works better than the Birchwood Casey, but hot blue is more trouble than I want.