Here are before and after shots of the worst corner of my awning this year. I made a mistake in the fall, got lazy and did not clean it before winterizing. Mildew grows on the accumulated dirt.
I used LA's Awesome... and its just awesome!
The process I used was to dilute the concentrated Awesome, spray it on the underside (make sure to wear safety goggles and old clothes), climb on top of my camper and spray it on the topside of the awning, roll up and let it sit for 30 minutes. Unroll the awning and wipe off with a mop and water. I used a ladder and one of those green scouring pads for the tough areas like this corner. Rinse top and bottom with a hose when done cleaning. Let dry and roll up the awning.