I like Bird's idea and leads me to thinking of building a wash bay where the excess water and grass can run off into the woods. Then just hook to a stationary pair of nozzles and stand back.
However, I keep my deck clean with a combination of mowing dry grass, a few hundred sticks that blow out of the trees into my lawn, and some hickory nut husks that rattle around in there for most of the summer from a couple dozen or more shagbark hickory trees. The deck for the most part stays pretty shiny. On the occasion that I change blades and run the tractor up on a ramp, I will take a wonderbar and knock down the dried stuff that sticks in the corners. But seldom get a full shovel of debris. Otherwise, I usually just clean down the mower deck and tractor with air after each use. Try not to use much water. Just my way, for what it's worth. /forums/images/graemlins/wink.gif