There are many ways to anneal cases, one fact for sure, it has to be cooled fast. Cases should be put in some sort of cool water to keep the convection of heat percipitating into the case head area. Some use a lead pot and dip the cases into the molten lead and then quench. I use the pan of water method as described in an earlier post. Factory annealing machines do the same thing, the cases move through an assmbly line of flames to get the necks dull red in color, they then drop off the line and into a running water bath to quench cool.
Brass or most non ferous metal are the opposite of Steel, annealing steel you heat and let cool very slowly. The more you work brass, ie, sizing, Neck forming, fire forming, results in work hardened brass that will crack or split. A lot will depend on the factory brass you are working with. When fire forming almost any AI type, annealing the brass first will increase case life.
Here is a link to a annealing machine.
Annealing brass cases
I am doing a lot of neckdowns of the large 408C-T cases, bringing them down to 338 cal is a lot of neck movment, i pre anneal the cases to soften the brass, we dont want it too soft. After the neck forming is done i anneal one more time, this time a little farther down the case shoulder. Then fire form the cases. When your working with 2.00 brass everylittle bit helps in extending the life of the cases.