"How do I know when I have lowered die enough in press but not too much to accomplish that?"
Get a candle and put a nice layer of soot on the case neck, shoulder, and a little down the case body.
Then back the die out so that when you run the case up on the ram you don't feel it contact.
Then, with the ram up, you turn the die back in until you feel it hit the case.
Then, lower the ram, and start turning the die in a quarter to a half a turn, and run the case into it each time. When you back the case out, you'll see how much of the neck has been sized by the soot that has been removed.
Stop when you have maybe 1 to 2 MM of case neck right above the shoulder with soot still on it, but you haven't removed any of the soot from the case body.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.