I've used the Zip-Dee cleaner and it works pretty good. You actually apply the foam (that is generated when you squirt water into the bucket of powder) to the awning and clean it that way. The awning certainly did look good when I was done. Problem is it's not easy to find and trying to buy it from the store at the Airstream site is prohibitively expensive, especially once you add shipping. I've been trying to convince my local Airstream dealer to carry it.
'04 Classic 30' S.O.,'03 GMC Savana 2500,'14 Honda CTX 700