6T2Burb, POR-15 doesn't have to be painted over or primed to be effective. The only problem with unpainted POR-15 is it will get a purplish hue after prolonged exposure to UV rays. If you don't mind a slightly purple truck, then no need to prime until ready to paint.
When ready to paint either use POR-15's primer first or just wet sand with 600 grit until dull, then use any primer and paint
