Primer

If you can get Farecla products in the US, you will find that G3 cutting compound machine mopped using a white foam G-Mop, will work extremely well on most paint finishes as well as gel-coat.

I have never needed to do anything other than wet flat final finish 2k paint with 1000, and then mop with G3 making sure that the mop head doesnt dry out.

Here is what I use for final finishing of a plug. Other than water and a few soft polishing cloths thats all you need. I wet flatted the plug in the pic using 1000, and then mopped using G3 compound. Took about 30 minutes, and the finish is pretty good.