[dubie]

it also depends on what spraying set up you have. You'll definitely need the 2.5 gallons of paint if you use conventional gravity fed or siphon guns. If you use a good HVLP gun or spray it through an HVLP turbine, you transfer up t 80% of the material to your surface. Conventional guns that spray at 30-50 psi only transfer 50% of the material, the rest is airborne.
You also have to take your primer into consideration. If you have your primer tinted to a color close to your base color, then you'll use less base coat.

The clear coat, it's always better to have more than less because that's a pretty time sensitive process. YOu want to hit your flash times bang on so buy a little extra. I would say 3 gallons of clear and hardener should do it.