Annealing, then resizing seems like the most intuitive approach.

The annealing video had you put the brass into a tall socket - just large enough to hold the case, and spin it on a drill while heating the brass from about 5mm below the shoulder up to the neck. They were heating them for <10 seconds, and the "done" test was how the brass changes color. The purpose as stated in the video was exactly what Jim suggested in the first response to my OP... to make it less brittle.