It is critical for any product to work the the surface be free on any rust, dirt or oil and if possible paint.
Well, I painted already. I am going to put the sealer over the paint. I know it is backwards, but I didn't strip the paint entirely. Just spot sanding and prime.
"Eastwood's high-solids Seam Sealer seals cracks, crevices and body seams, as well as waterproofs and insulates; remains flexible.
Adheres to paint; tack-dries in 15 minutes, air dries in 1 hour. Black in color, but can be painted after 1 hour. Use a standard caulking gun to apply."