Hot Rod Magazine shows you how to use body filler, ... That's wherelow spots in the surface still exist, requiring more filler. So it's back to the mixing board for a bit more.

We used to do it the same way we tape drywall, by applying five pounds of body filler and then sanding off 4-9/10 lbs. ... Spread the filler down the mixing board in an S-shaped curve.

Other supplies you'll need are 50-, 80-, 180-, 220-, and 400-grit sandpaper, body filler, mixing board and spreaders for the filler, and spot putty.