Worst to worst, primer in a 1 gallon can is pretty cheap, compared to paint, and since the truck will be all taped off it wouldnt cost all that much more in the grand scheme to just prime it as well. I tried taking mine to the primer but ended up going to far in enough spots to justify the extra 40$ can of primer. Plus primer is great for cheapie dent repair.
I am redoing mine now, because of trying to do it cheap and on the fly, and as soon as I hit it with the first coat of paint I knew it was getting sanded off because of to many small little spots that priming and a few extra minutes would have fixed.