I would not warm my mold with the teflon pins installed.
The reason you pour blanks (no hooks) with the pin installed, is because a lot of lead will stream out of the pin opening on some molds. You might end up with a lot lead on your table and a incomplete pour.
There is no set time on how long you keep your mold on top of your pot, also there no set number
of how many blank pours you do.
The goal is to warm(hot)the mold, and to get good complete pours.
Some people warm their hooks in a tin, in a toaster oven.
Too hard to place hooks in molds with gloves on for me, that is why I use a propane torch with cold hooks in the narrow parts of molds.
Good Luck. I know you are a Delta Guy but lets hope Clear Lake(all California lakes) fills up with all this rain!