"something like 15 minutes at 660 degrees"
Heat travels to cold, in 15 minutes at 660 degrees the head of the case will be annealed and too soft to be used. There are some that use a candle, I can not imagine how long that would take, to cut down on heat travel use high heat for a short period of time.
When holding a case in the hand when annealing if the case gets too hot to hold, the case got too hot, again there was a demonstration of annealing using the finger thumb method, the demonstration hardly got started before the hand disappeared and the demonstration continued without an explanation and the hand is no where in sight.
A heat dam works and prevents heat from traveling, deciding where to put the head dam has not been decided, some say shallow pan with water, how much water is never decided, water boils at 212 at sea level, if the pan is deeper and more water us used when annealing a spheroid condition can be observed when the case gets to 212 degree, meaning the case is too hot to allow the water to remain in contact with the water, the boiling water indicates the heat on the case is being given up to the water, again an increase in volume and heat will shorten the time required to anneal the neck, if the cases are to be formed, the case should be annealed to the point the shoulder is formed.
F. Guffey