I think it's way easier to paint the bottom side of the car in the factory primer overspray method. It IS how they came new! No time consuming masking, and heck of $ savings in paint materials! I want to puke everytime I see a car full painted body color underneath. The ironic part is after restoring it incorrectly they add paint dabs and parts tags to detail it up. Why bother, it's incorrect from the get-go!