You can find etching primers in spray cans.
Rust-Oleum would be the cheapest.
I had used the Dupli Color on a motor I
wanted to do over as it was getting a little
beat up from use. It was a real pain to get
off before I could start over. When aluminum
gutters first came out they weren’t coated
like today. Painters would acid etch the
aluminum with vinegar before the lead
paint was applied.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.