Morris, see about getting real black primer. It'll probably cost you the same in the long run and will come out better. Trev is right, only use the fan tipped if using cans. Best to do only one panel at a time w/ cans. Otherwise you'll see streaks if you shoot the whole side at once. IIRC, Advance has semi gloss black in quarts and HF has cheap guns.
Maybe I'm stupid, but I always set my pressure to about 30-40 PSI no matter what gun I use and it comes out nice. Then again, I'm by no means paint and body guy. Perhaps ingorance is bliss.