Michael Gross wrote:
Bear in mind that the process of hardening and annealing brass is exactly the reverse of that used with steel: brass is hardened when it is heated and allowed to cool slowly; it is softened or annealed when heated and cooled suddenly.
Speaking as a metallurgist, this is certainly not true of everyday or common brass, 30 percent zinc in copper (yellow brass). Heating rate won't matter, and cooling rate will matter little either, with slower cooling making for either no change, or softer brass.
Of course there are lots of alloys commonly called "brass" (maybe even some that can harden on slow cooling), and to make a general comment about "steel" is even worse. From the mild steel you buy at the hardware store, to high strength technical alloys, is a galaxy of difference.
Heating brass to red heat and setting down to cool in air is what I would do to soften it, if it's yellow brass. And I wouldn't even do that if it isn't very hard to begin with. Small diameter brass wire normally is cold finished and hard enough to benefit from annealing, but it may already be partly or completely softened in processing before you get it.