brass doesn't need the air cool to harden, it is non ferrous and thus is hardened by work. You anneal the metal to soften it. to harden it when it is non ferrous is to actually hammer bend or other wise mash it. You can also sand blast it to harden it. Just heating non ferrous again, makes it soft, and that is not what you want. To clean it after you have worked it, get a small pot and some strong vinegar, and let the pieces sit in hot (just about boiling) vinegar. This will work in a pinch as a type of pickle. If you have access to swimming pool acid that is even better. Pickling metal cleans it of any surface impurities that you get from annealing and working it. For those times between annealing and working, just use a spray like 409 (kitchen spray cleaner) to de grease the metal. I would go with either an 18 guage or smaller size. In metals decending numbers means thicker metal.personally I would be working with some of my old 14 guage, then if I needed too, I could smash it thinner to work harden it.