I do not know about the "lead pot method", so I won't comment on that.
I was taught to use a regular old plumbing torch to anneal the neck on bottle neck rifle casings, and this method needs to be done outside.
Do this at your own risk ON CASES THAT ARE NOT PRIMED.
Set up your torch and have a catch bucket under the flame.
While holding the cartridge by the head (and perpendicular to the flame) rotate the neck of the cartridge in the flame until you just start to feel any heat.
Drop the cartridge in the bucket.
The neck is now annealed.
It is simple, but it works.