The temperature that cartridge brass must be heated for annealling is 762 degrees. I use 765.
I don't bother with torches, too complicated. I use my lead furnace and a casting thermometer. Heat the lead to 765. Get a bucket of water, clear of the furnace. A cup of cheap oil is handy, dip the case mouth into the oil to keep the lead from sticking to the case. Dip the casemouth into the oil, shake off the excess, dip the case mouth into the melted lead. Rifle rounds can be help in the hand, better use pliers for handgun cases. Watch the brass, there will be a color change, the brass will turn a bit darker. When it does, drop the case into the bucket. Some ice in the water means I don't have to stop and change the water.
Once I have everything set up and I get into a rhythm I can do a case every five seconds or so.