As with any paint or coating, prep is everything! Surface must be clean, de-glazed of wax or other protective coatings, sanded, dry, etc.
Be sure the product is for the surface you are covering and follow the instructions of the new coating.
I would plasti dip them its the easiest and cheapest way. Plus if you want to redo them in the future you dont have to stip the old paint or any of that and you dont have to tape any thing off with plasti dip it just peels off its great!