undercoating removal

I usually only remove it where it isn't bonded well, usually because of impacts from an accident, rocks, or corrosion. In that case, it often comes off in chunks when you pry under it with a putty knife. Ditto for the similar black "seam sealer" on the inside (trunk, under dash, etc). To remove residual, I wipe with gasoline. Mineral spirits is safer, but have you priced it lately. Definitely not a choice for smokers.