Use a 800 or so grit paper, than finish off with a 1500 to smooth any burrs outs. After you prime it, sand the primer with 1000, prime again, and sand with 1200. When you paint it, do light coats, sand with 2000 between each coat, and you should be good. If you're going to add a clear coat, you NEED to sand with a 2000 grit paper between each coat of clear, or it won't set right and it will flake up and peel off in no time.
Take your time, get all the areas, you can only get back what you put in.
And DON'T wax the newly painted surface for about a month. Many people will tell you it's ok, and it's not. Turtle Ice or some other type of liquid wax is alright to use, but don't use a paste or polymer wax, it will scratch and swirl the not-yet-cured paint/clear.