For a trailerable boat, a scrub brush and some bleach is a decent start, oxalic acid is good too but you need to be more careful. It will take a couple of goes at it to get it done fully.
Marine cleaners: Collinite (collinitemarine with the usual .com and such) That stuff really works and well. Make sure you get the wax too. A good cleaning and wax job will truly do wonders and will last about two years.
Galvanized trailer. Usually not. Spend the money on making sure the lights, wiring and tires are in good shape as they tend to be a bigger source of failure. Now, if it's really rusty, obviously you have to deal with that.
Antifouling paint. Think about how you are going to use the boat first. If it's going to sit in the water, antifouling paint is a fine choice. But if you launch and retrieve the boat each time and our out for a few hours or a few days, this really isn't worth the cost.
Hope that helps.
The sea is always beautiful, sometimes mysterious and, on occasions, frighteningly powerful.
Last edited by Maren; 06-14-2011 at 10:39 AM.