I have tried just about everything you have been told to do except the special primers for aluminum. Nothing has worked very well. Now i just buy 3 or 4 cans of cheap green,brown and black paint. Sand and scrape any loose paint off. Wash the boat off. Then touch up or repaint as needed. The worst places are ussauully the floor and the bottom of the boat. It is a little 12 footer and I paint the bottom because sometimes i will prop it up on sticks and use it for a blind.