There is no reason an airless spray gun would not work to propel primer onto a hood or fender.
It'll possibly look like a giraffe diarrhea splattered on it, though.
That's probably not the best description, but I've sprayed all sorts of stains & primer & paint through those 'Wagner-type' airless guns. If you just want to coat the metal, it will work just fine, but it will sort of dry to a leathery texture.
Subjective statement: I know you asked if it will work; it will, but it will not look very good.
Brad
Nothing a good belt sander couldn't take care of though...
Actually a simple RO pad sander and some 80 grit work better, but if it turns out like TANNED leather, well maybe the belt would work.