tips for spraying primer

Dave, that's an all too frequent occurrence when a novice listens to the "paint store guy". :) I still print out a copy of the P-sheet for everything from epoxy primer to clearcoat and have it taped up at my mixing table each time I use the product - and I've still managed to blonde moment a few mixes over the past 40 years. :)

Matthew, without actually seeing the car, I can't really tell you if a coat or two of thinned urethane will fill those solvent pop craters. If all the damage is from solvent pop, then it will be worse on the hood and trunk lid, just because that's where it gets put on thickest, and I imagine that would hold true for a roller as well as a spray gun. If it smooths things out in those two areas, then the remainder of the car should be a cake-walk.

What type of spray gun, and what size nozzle and tip are you using? This could make a huge difference in how your 4:1 primer sprays out also.