Rich, really depends on how cold it is in the garage when I am pouring the lead. Like you said, the idea is to get the mold heated up. I tried the propane torch a few times and it really did not seem to get the molds heated up right. First few jigs always came out with wrinkles
Seemed to work better for me just doing the test pours. I judge the amount of test pours based on what the head looks like when it comes out of the mold. If I'm only doing one style of head in a melting session I put the mold on top of the melting pot as the lead melts. Seems to work well. Usually do one test pour to be sure and I'm off pouring. Will give the propane torch suggestion another go next time I'm pouring.