Painting steel step bumper

[ItWillBeSlow]

What's the best procedure for painting an Oem steel step bumper?
I plan to go with argent silver. I originally thought i would put a coat of por15 down and spray a coat of rattle can silver. Should I skip the por15 and use rattle can primer instead? Vht and Eastwood both have the argent silver, is there a differences? Both companies also suggest a clear coat, is it necessary? These paints are marketed as wheel paint, I assume it will hold up to the occasional step on the bumper