I was checking out your build and read the part about the tailgate with 10 layers of paint and I have a solution for the next time you run into something like that.
This is a Polycarbide abrasive wheel it will strip, heavy rust, paint, body filler, it tore right through heavy scale rust on my cab and didn't even blink, but it is gentle enough that it won't remove any metal and leaves a nice clean surface.
https://www.harborfreight.com/4-1-2-...eel-94017.html