The key to annealing so you dont get them too soft and have the shoulder buckle is to hold the rim in your fingers lightly, run the propane torch over the shoulder and neck (no lower) while rotating. When it gets too hot to comfortably hold onto drop quickly into cold water right by you. Once you know the time it takes to do this with the flame you are using, and how they look in the room with low light, you can hold them with a small tongs and save your fillangees.
You may want to overheat one to glowing and water drop, then resize to see how a soft brass folds up.