My old boss in Phoenix said to always use a heat gun on old filler before sanding, but my new guy says that's a waste of time.
I worked at a shop in Phoenix for five years, and the manager there drilled it into us: 'Hit any old body filler with a heat gun for a minute before you start sanding, it softens it up and saves your paper.' I did it on every repair. Then I moved to a new shop last month, and the lead tech saw me doing it on a '98 Ford F-150 quarter panel and just laughed. He said modern fillers don't need it, and I'm just adding an extra step that bakes the shop. He told me to just go straight to 80 grit on the DA. I tried it his way on the next job, and honestly, the sanding did feel a bit harder and I went through two more discs. So now I'm stuck between two methods from two guys I respect. Has anyone else tested this out and have a clear winner?