well where do i begin....
the coats on your car from the factory are a follows
1) epoxy etch (crosion protection)
Im not sure how Dupont is but i know the paint i use needs 3 coats of base and 2 coats of clear. You would only need the epoxy etch put on if when its sanded it'* sanded to the bare metal. Contrary to what some people think you dont need primer to get the paint to stick
its only put on to fill sanding scratches from body work and any other heavy sand scratches (120-320) the paint will stick to the old paint provided that its sanded with atleast 400 but it'* best to finish off sanding with 600-800.
the yellow seen on sullys car is not sealer (i beleave) its the color of the old plastic used i may be wrong on this one because im not sure they still used the yellow plastic when our cars came out
if i missed anything or you have more qustions just ask