Peel Stop Paint Primer is how thick it is — three times thicker than a standard primer, according to the maker. You can lay a heavy coat on a vertical surface without any sagging, and smooth over weathered surfaces. As a binding primer, it’s supposed to glue down minor peels and other defects (though you still need to scrape and wash the surface). You can top-coat it in two hours and use it under or over any oil- or water-based top coat. It costs around $35 per gallon.
Rust-Oleum, 800/385-8155, rustoleum.com.