The rough surface will result in a non-smooth/non-glassy final finish. If you prime it with a thin primer-sealer, it won't hide the roughness, if you want a smooth finish, you will need to prime with a primer-surfacer that is intended to be sanded, then more primer until you have the desired smooth surface on which the topcoat will sprayed. My opinion on powder coat is that the plastic envelope that is created will hold water under it and rot out the steel. Just my 2 cents.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy