You don't need to primer them unless you're doing work on them. You'll probably only need about 2-3 Spray Cans (if that's how you want to do it). You can buy clear coat in a spray can from an Auto Paint Store...I think SEMs or 3M makes it. All you need to do is sand them with either 320 grit sand paper, or a Red Scotch Brite Scuff Pad (by 3M).