Painting question.

[eighteenninetytwo]

My truck is dark blue. Most panels have dings and dents in them which i have sanded down and sprayed primer on where the paint is cracked and there was rust showing a bit so she looks a bit of a hodge podge. Ideally - in time, she will have new panels added and get back to her original GMC crimson red with white side bar. Currently i have the tailgate stripped out and I'm going to clean and put back together. Is there ANY point in priming properly and doing a decent job now of crimson red on the tailgate? bearing in mind that painting the truck as a whole is not something is can do at home and i will need to have a respray done professionally at a later date. Ok so I just answered my own question - no point. Moving on.
what do people use for frame and under wheel arch paint? rustoleum, or that rubberised noise reducer paint ro something else?