OK, guys, this is new territory for me too. Have you ever heard of treating bare metal with a phosphate wash before mud or primer? I have D.P'ed (epoxy etched) all raw surfaces first, then after metalworking back to bare again, I touched up the area with a wipe/wash that makes the surface etched. Also what about using a fiberglass filler? Are they truly waterproof as I have been told?
I also have been instructed to use a primer/sealer over all finished bodywork-?