Is it good to heat up the exterior wood stove metal with a propane torch right before spraying on the high temperature paint? See video below!
The video you uploaded. The reason I believe someone would preheat the metal prior to painting would be in a cold climate or temperatures below what the manufacturer recommends to be painting with there specific paint. Most paint has a specific temperature range that the paint will flash off. Read the paint label on your paint can and go from there.
I will say that I find rattle can paint sticks to metal much better when you preheat the metal.....just enough to watch the "humidity ring" evaporate from the item that's being painted. I just did this to the rims on that old supersplitter I bought last weekend, cleaned all the rust off of the beads, warmed the humidity off of them and gave them a good coat of paint inside. Was dry and ready to go in minutes.
I've seen guys in the painting dept. at the shipyard(s) do this, supposedly to drive the moisture off more than anything. Even if it had just been sandblasted.
When they pulled the stove out of the shed it was rusty and shabby. The even replaced the door gasket. Also they used an angle grinder with a flap pad. I have done that so it is nice and smooth so after the paint it does look brand new. The torch looks just like this Harbor Freight one? Propane Torch with Push Button Igniter