There's a lot more to painting correctly then just spraying primer and paint on a frame or anything to be painted. First not only do you have to sand the frame but, degrease it before you do anything. then thoroughly clean it again with solvents such as acetone or denatured alcohol. That will remove any residue left behind by cleaners. You'll get much better adhesion. Then you can do as Taolc-kdx said. He definitly seems to have painting experience. Pj1 epoxy paints are as good as you get from a spray can. any good paint will go on thin. Try painting a car, automotive paints are super thin. So are 3 part plastic paints there like spraying paint thinner. Also, something else I almost left out, humity and temperture also pay a huge roll in spraying. That information is on the can of Pj1 paints. If you want the most durability, send it out to be powder coated.