Paint not wanting to stick to lip?

Hey Guys! Long time since I made a new thread but I seem to be having trouble with color matched spray paint wanting to stay on my lip. When I got the lip I sanded it all down and made sure it fit, then cleaned it super well. After that I primered it with filler primer, which I then sanded down again with even finer sand paper. After cleaning it again I sprayed a couple coats of the paint on and then a couple coats of clear. A couple months later the paint appeared to have bubbled a little then flaked off, so I sanded that spot down and then filled it, and then repeated the whole process again. Now a WEEK later it's already starting to bubble and flake off again. Any ideas on what I'm doing wrong or whats going on? I thought it was moisture under the paint but on the second go I made sure that it was bone dry, so I don't think thats the issue.

No matter what type of paint you use, normally when you spray anything other than metal you have issues with adhesion. There is a solution for that, aptly named adhesion promoter. If you have a decent auto parts store with paint and body supplies, they should carry it. If not, your local Sherwin Williams paint store (not in a Lowe's or home Depot, a stand alone store) should carry it. If all else fails you can ask a local paint shop where you can find some.

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^ Thanks for the advice! Ill definitely look into it!

Update, a few years later. Adhesion promoter was 100% the answer.