For washing finishers forget hot water and get the biggest (gpm) washer that you can supply water to.  Hot water gets things cleaner but when you can't see anything I think hot water loses its advantage.

3000 psi is plenty of pressure, more gpm is what gets you done faster.

Sprinkling is the key to making washing easy as possible.  Running sprinklers continuous works fine but puts too much water in the pit, putting the sprinklers on a timer will do just as much good with 10% of the water.

Some temp controllers are capable of running sprinklers or you can use something like an Edstrom or even just a lawn sprinkler timer.