Paul,
If I remember correctly, brass is the opposite of iron based alloys, with iron you heat and then quench to harden. If you heat and let aircool it anneals or softens the iron and allows you to bend, drill, file, etc.
With brass is an alloy that can have a number of different mixtures and characteristics. If believe that in general you heat and quench to anneal. Reloaders often heat and then quench the mouths of cartridge cases to prevent work-hardening from reloading causing cast mouth splitting.
I believe that so-called "German Silver" is a complex nickel-brass alloy that has a number of varieties, some of which can be a bit brittle. I think that is I was trying to rework cast "German Silver" I'd do like you are doing----ask.
If I failed to get informed responses and had to proceed anyway I'd probably heat and quench it, like brass, rather than heat and let aircool.
