Curious- base coat vs acrylic urehane for base

The car I am doing is a 62 Lancer, smaller than a duster lets say. Doing the jams, eng. compartment, under truck lid, NOT under side of hood not inside trunk. If I did this while car in single stage, 1/2 gal. urethane (4:1) would do 2 coats for sure. I agree I shold do the bc/c deal. Would 2 qts of base do it????? B3 Ice blue poly. Figuring on a grey epoxy sealer under it.