I was taught to anneal brass, copper, and aluminum by my dad, who occasionally did bodywork on brass-era cars.
Take your oxy-acetylene torch (remember, you're in a body shop...) and start it up on acetylene only. Soot up the surface of the metal with the torch until it's evenly blackened. Then turn on the oxygen to get a neutral flame. Use the flame to heat the metal until the soot just disappears -- when the soot burns off, the metal is at the right temperature to anneal, and you move your torch to the next spot. It should air-quench* plenty fast to soften.
You could probably soot things up with a candle, and use a propane torch to do the annealing -- you'll have to try that part yourself if you don't have an oxy-acetylene set.
* non-ferrous metals harden and soften in reverse from steel: with steel you make it hard by heating it up and cooling it quick, to "freeze" the crystalline structure in place, and you make it soft by heating it up and cooling it slow, to let the crystalline structure relax. With most alloys of non-ferrous metals, you make it soft by heating it above its critical temperature and quenching it, and you harden it ("precipitation harden") by holding it at elevated temperatures for a while. It's all voodoo to me -- I just repeat what I've heard from folks who actually know: except it seems to work.