Red Oxide Primer..

[ORIGLS6]

If you're trying to remove undercoating/sound deadener, I highly recommend the good old Kerosene and paintbrush method. Apply with a spray bottle, let sit overnight, scrub with the soft brushes and wipe down with rags,.......repeat, repeat, repeat! For normal road grime and the like it's hard to beat Simple Green or Krud Kutter. But probably the MOST important item is PATIENCE. Soft brushes are key to retaining the original finish and markings. It takes longer (much, much longer) but you'll be happier at the end.