I rinse my tractor off pretty frequently. Dirt and dust hold moisture against the paint and metal. I've had my tractor for three years. I've washed it twice with soap and water. Just do the same thing you would with a car. I've waxed the painted surfaces once. Just use a basic automotive wax. I know a lot of hard core tractor folks think that is funny, but there are several things to consider. First, my tractor basically lives outdoors, just recently built a shed for it, but even that has open sides. A wax job once every few years will probably go a long way to protect the painted surfaces. Second, good paint helps resale. If you doubt that, look at used tractor classifieds. Many if not most will comment on the paint. Buyers care.....even if they say they don't. Third, I find that in general I take care of something a lot better if I feel good about how it looks. Maybe that's just me, maybe its human nature.