I have had pretty good results from this process, so far. It takes prep work to do it up nice, but rough finishes will come out looking "tactical", as long as they are clean. You need:
A propane deep fryer, or similar propane stove
A really big pot, NOT ALUMINUM! And avoid stainless steel pots, too, as they tend to use aluminum rivets to hold the handles on. The salts will react with, and dissolve aluminum pretty quick. I tried ss, once, and the handles fell off. Use old school enameled steel pots.
Ammonium Nitrate. It comes in instant cold packs, but in insufficient quantities. The way to buy it is prilled as fertilizer, search for "34-0-0 fertilizer". Or, potassium nitrate (stump remover) can be used, though I haven't tried it. One advantage to that is no off gassing of ammonia, which the former will do vigorously. Use a good gas mask, and do it outside. This is the same chemical reaction used in clandestine meth labs, so it smells like a meth lab, and you need to ask for these things the right way, or they'll look at you funny.
Sodium Hydroxide, aka Lye.
The recipe is 2.5lbs nitrate to 5lbs lye to 1 gallon of distilled water.
You might need more than one gallon, and you'll have to add water to it (very slowly and carefully, it will boil vigorously!) now and then, particularly when you cool it down and store it. The lye increases the boiling point to as much as 300 degrees. This is a great help, too:
http://www.guntechtips.com/bluing/bluing.htm
