Sand the entire surface with a light grit sandpaper, maybe 120 - 320 grit. Once the entire surface has been sanded, use a tacky cloth to wipe the entire surface after, of course, wiping off all debris and dust. Once it's been wiped off by the tacky cloth, grab your primer. Spray on primer, sandable, just about any primer in a spray can will do, I use the grey color. Primer dries quickly, much quicker than paint. The idea of applying ANY coat of paint in this manner is to make sure you lay your next coat while it is still "tacky", it shouldn't be completely dry as you want it to adhere to the previous coat and not just cover it. A good practice is 3 coats of primer, wait for it to dry and give it a light sanding with 320 or higher grit paper, then apply your paint/color. Number of coats for your color depends on how many you want. At least 3 coats of color, I wouldn't do any more than 5.
This method has proven itself over and over again. I used this method on my front grille and it is going strong for over a year without even one chip. I used Dupli Color gloss back. You may want to consider wet sanding or clear coat, especially if it's interior, but ultimately up to you.
Hope this helps.
Snorkel Delete / K&N E2993