The Great White Brick - '69 Valiant
30 years? I was thinking like 100! Both sides are sandblasted then Por-15'd and there's still some oil spray sandwiched in between some metal-on-metal areas.
To scrape off the undercoating I'm using a big tough automotive scraper (it's like a screwdriver but the tip is very large, I just keep grinding it sharp), an old paring knife with a curve on it (but it broke last night, gotta find a new one) and a wire brush. Later I'll attack the residue with some WD-40 and wire brushes, then some degreaser and brushes again.