Here's another twist- If I don't have time to fire up the hot blue tanks, but need to protect a bare steel part I "hot/cold" blue it. Started doing it many years ago on sights I had just worked on. Degrease thoroughly, glassbead if wanted (works great with a removeable/dovetail front sight) heat with a propane torch - probably 400 or so degrees - and lower into a pan of Brownells Oxpho-Blue. Make sure it's quickly and completely submerged. After a few seconds lift out, wipe off and oil. Nice and black and pretty durable.
Now here's the interesting part: with a complete slide, polish, degrease, and with a wire hanger supporting it, heat and dip, etc. If the basic finish is not real shiny, you get a finish that will easily pass for a hot dip blue. Works best on, say, a 320 grit finish maximum, and it's crucial to degrease thoroughly.
Great if you're going to do a few weeks' testing on a gun before final finish, but for a do-it-yourselfer, not a bad option. BTW, you may NOT want to breathe the fumes!
Armco Machine & Plating