I've done the POR 15 to cars and trucks in the past and it works really great. It is all in the prep and you can't cut corners. I would wire wheel any surface rust (you don't have to remove all of it), use the Marine Clean, followed by Prep and Ready, and then finally the POR 15 paint. Be sure to wear gloves and a long shirt, that stuff is super hard to get off of things!!!
http://www.por15.com/
Their home page shows 'new' spray on chassis coat aerosol cans. Ooooo.
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Praise the Lowered
67' Camaro - Worked 327, Hotchkis TVS suspension, 4 wheel cross drilled discs, AM radio FTL
05' Silverado - Stock, stock, and stock.