[troy-curt]

Willy 36 has got you going in the right direction.
Don`t get the filler wet. If you do, Use a heat gun.If you want straight sheetmetal stay away from a torch.My self I use 120 gold 3m dry paper in a roll.
When the filler starts showing through the primer, you should be done, If the area needs more blocking, shoot some more primer,let dry , start blocking again,keep blocking untill lows and highs are gone and no filler shows. Exp. is your best teach. Good Luck