The idea of painting all the hidden areas first, then assembling the car to paint the car whole sounds good.....Except for the overspray. Paint and clear will get through the gaps between the fenders/doors/hood, etc. So now what? Do you attempt to mask off the door jambs? Sure, masking an engine bay isn't that hard, same goes for the trunk.
How would a painter be able to assemble a car and shoot it all themselves? I'm talking about every area, no "Pre-paint" type of technique. Can this be done by one person without getting dry edges?
I've always painted metallic cars in whole in the effort to get consistent color match. I am not a good enough painter to do otherwise with a metallic.