I would recommend you buy some of Southern Polyurethanes epoxy primer. Over reduce it so it flows out. Use their hot weather reducer. Roll it on with a two or three inch roller (one not made of foam). Use a chip brush to reach spots the roller can't get to. That will seal it better than a wash primer. Wash primer is porous so it needs prompt top coating to lock out moisture. If the metal prep is good, you can block sand the epoxy later on and continue. If the metal prep isn't finished, whatever you use all needs to be removed when you pick up where you left off.

If your prep is complete, another choice would be to take your project to one of those shops who spray out $300 paint jobs. Their painters do a decent job spraying paint. Bring them name brand epoxy products and pay them to spray out two coats of your epoxy and ask them to discount the job $50 or so from their materials cost.

Whatever you do, stay with automotive paint products unless you're taking it back down to bare steel later on. I have a friend who used Rustoleum fish oil based primer on the rust prone areas of his Datsun before spraying on Dupont enamel. He thought it would be better at preventing rust than Dupont's automotive primer. Within months, each of these "specially treated" spots was molting large flakes of paint. He might as well have top coated over wax.