Heat the part to betw 800 and 1100F and let it cool.
Yes you can also dunk it in water to cool it off quickly,,it makes no difference in the final state the Brass will be in.
Brass doesn't anneal or harden by heating and quenching as steel does.
Cooling quickly lets work get back to work quicker that's all.
That heat range will be right in the eye-ball range of starting to glow dull red in a dark room or corner of the shop.
Not very precise,,but will do nicely for making brass parts for M/Ldrs.
(I don't even go that high when annealing cartridges,,just a few seconds with the neck in the torch flame and let them cool on the concrete floor. More of a stress relief I guess.
No need to go any hotter than the 1100F for annealing. Certainly no where near the melting point of Brass alloys.
The brass alloys have a melt temp of somewhere around 1600F.
So you are far from melting the part when doing a simple annealing.
There are a dozen or more alloys of 'Brass' I'm told, different %'s of copper, zinc. Some with lead and/or tin added as well.
They all likely have a precise and different melting temp ..as well as a very precise lab spec anneal temp.
But for our purposes the above method will do.
Those cast 'Brass' parts can be of just about any alloy as they may be done up with scrap brass and combined alloys.
Some of them are terrible to work with especially engrave unless they are first annealed.