If I was doing it I would start with 180 grit paper than 300, 500 and 1000. Than wet sand with with 1500 and 2000. You could keep going up but 2k is enough in my opinion than clean it with an all purpose cleaner. I'm not familiar with the product your using but if spay an adhesion promoter on the surface first! If the product doesn't have a promoter mixed in. Follow the directions you should wait between 5- 15 minutes between coats. Lastly clear coat never hurt anybody spray some on if you want to it can only make it better.