I'm still involved with the county 4H fair, even though my kids have been out of 4H for 6 years now. Every summer, I take my tractor and manure spreader to the fair so that the kids can keep the barns clean. Before I take it over, the entire tractor gets "detailed". Even clean up the spreader!
The two older tractors don't see water unless it's raining. They have a protective layer of dirt and grime that's almost like an armour plating.
The Deere that gets cleaned was recently repainted. I'm debating painting the old Massey 150 this winter, then the Ford 300 NEXT year. Only problem is, then I'd have to wash 'em once in a while.