I usually use a car wash like great white
mentioned. As far as applying wax, this past summer I tried a couple of the Protect-All products. I really like the results.
Here's a link to a thread I posted after using Protect-All for the first time.
What I use to clean the awning, I add about a ¼ cup of bleach and some Dawn dish washing liquid to a couple of gallons of water. I spray it generously on the awning, roll it up for at least an hour, then unroll and rinse off. Usually I can easily brush off any stubborn areas. As you mentioned, leave the awning out until it completely dries.
Hope this helps you.