On street rods where they want to omit the fender welt we "butter" the body with Allmetal where the fender flange bolts on and put a strip of wide duct tape on the fender flange making sure it's wrinkle free. While the Allmetal is still soft the fender is bolted on with every bolt which is snugged to near final torque. The excess will squeeze out and can be trimmed easily while still soft. When cured the fender comes right off because the filler won't stick to the duct tape and with the fender out of the way the filler can be blended to the body and sanded smooth. Once painted the fender to body joint is virtually invisible.

Evan