when i paint my plastic interor parts i do this process ....
1.Remove all pieces u like to paint
2.wash all pieces with dawn dish soap, rinse then dry
3.spray "Bull Dog Adhesion promoter" or a different brand
4. spray 2-3 LIGHT coats of desired color from "Krylon truck and SUV paint"
5.Spray 2 coats of "Krylon truck and SUV CLEAR COAT"
and there it is
hope this helps as i learned it from a diffent forum about 3 years ago when i had my Hyundai Elantra