My boat is a 14' Lund aluminum v-hull. Got it last May. Looked like this when I picked it up:
Like you, I wasn't looking for a "show piece". Just decent, and not expensive. I read about an RV trailer rehab that used Krylon Farm and Implement paint with a hardener added. They also used the "roll and tip" method.
So I stripped the boat mechanically with brass wire wheel and abrasive disc.
I still need to clean up the bottom, but that's a project for next winter. Here's how it sits now:
I bought the paint at a local auto parts chain store. I used half of the quart to do the whole boat. Paint was $15. Total cost of the job, including rollers, a brush, and some thinner was less than $40.