This is a good video on how to mix rap vocals like a pro by Raw Technique Studios. The tutorial is quite basic, but it provides a very good starting point if you have never really worked with Rap vocals before.
Paying out for an effective PR campaign can be an expensive ordeal and in some cases offer little return for the artist. However, there are plenty of tools and ways you can run your own campaign cost effectively.
Music distribution has shifted in the past decade for the benefit of independent artists and labels. RouteNote are leading this transition.