Underbody best finish
That looks like factory undercoating, or the car got rustproofed at Ziebart when it was new. Either one is tough to get off! I'd do just like you plan to do, with the epoxy primer and raptor liner. No need to use etch primer if you're using epoxy primer. Like mentioned above, just make sure all of the weep/drain holes are open....especially the ones where the quarter skins weld to the rocker panels. It's gonna look nice when you're done!
:thumbsup: