So I finally have the firewall holes welded up and the trans hump transition welded and shaped. Infact I had to cut up the firewall about 1-1/2 inches at the trans tunnel then shape and hammer fit another piece of sheet metal back into that 1-1/2 to go from round to flat at the top of the trans tunnel area.. Anyway I've gotten the firewall finished and ready for bondo so here is my questions, I've sanded, power wire brushed the metal and now ready to move on to the next step. Due to heavy pitting I want to do some bondo smoothing to fill those pits and where I filled holes so should I use like rustoleum rusty primer or rustoleum rust reformer first then come back with the bondo on top? Plans are to use auto base/clear later down the road to paint the firewall. So would I be safe to use rustoleum rust spray bomb, bondo, then filler primer then later on base/clear?