We did the discussion a couple months ago, you can check it here http://www.gwtwforum.com/index.php?topic=4339.0
I don't know if a consensus was reached, my preference is to just hose it off, don't use one of those spray nozzles that'll shoot two yards away though. I would release the leading edge tension and leave the standoffs out to detension the sail but leave the lower spreaders in to hold the sail open for quick drying. The shower is fine and preferable should you have a water softening system in your home. If you feel the need to use some cleaner dish washing detergent is a good mild choice and was recommended in my fabrics classes for use on any delicates and dry clean fabrics as the best choice. Something cheap with no added lemon oils, fragrances, etc. just pure detergent is best.