Whoops, I linked the wrong product. I meant to link to one for metal.
Bulldog, okay. I probably will sand, though. But I keep getting ahead of myself. I'm not a painter, and I haven't found one yet for this job. I'll do what he prefers; or maybe wants to do it himself. I'll mention Bulldog.
Ya always sand but sometimes it difficult to get everywhere. Another product is Flash Bond XIM. Been around forever. Might have some compatibility issues with some products. Its like sprayable glue.