Diesel fuel and flat scrapper seems to be the best on under coating. Sure a blaster can take it off but We try to lossen it up and scrape off the big chunks before we send it to the blaster. I think on our next full tilt project I'm going to dip the car and then blast it right before we epoxy primer the car. The blasting is such a rough process, plus it open up the metal and the surface rusts faster then a dipped body.

Just another opinion.....