Originally Posted by Jerry Bransford
Coin-op carwash high-pressure soapy sprayer & a little brush action.
That works too if you don't have a powerwasher at home. With red Alabama clay, it is pretty much a requirement down here. In California, not so much.
Just make sure if you lay it out to wash, you lay it down where the ground is CLEAN, otherwise the underside will get nasty (assuming you're removing the top, duster, etc).