This is impressive! I will have to try itI have used this method for the past 40 years.
Put a lead pot on the stove, open the kitchen window and set up a draw fan so you're not breathing the lead fumes.
Dip the case neck and shoulder into mica dust (motor mica) then gently holding the rim of the case with a pair of pliers, hold the case vertically, then insert the case neck and 1/2 of the shoulder into the molten lead.
Depending on lead temperature and the brass itself, the neck/shoulder will need to be in in the molten lead from 5 to 10 seconds, then immediately dropped into a bucket of cold water.
When shortening and necking 22 hornet brass down to .14 caliber, immersion time is 5 seconds.
When making 219 Donaldson Wasp brass from 30-30 cases, immersion time is 7 seconds.
444 Marlin brass necked down varies from 8-10 seconds...
And the purpose of the mica dust is to keep the molten lead from sticking to the brass.
It takes less than 45 minutes to anneal 100 pieces of brass.