What you need to do is extend the awning stow position higher on the coach to clean the slide. My coach also has a passenger side slide and the only thing preventing me from extending or retracting is the length of the pull strap. With the slide out and the awning retracted the pull strap ends up above the slide and I can't see or reach it over top of the slide.
Here is the big picture my setup slide in, awning retracted -
The original extensions were painted carbon steel that were rusting so I hit up a local metal shop and had replacements made from stainless.
The awning is actually roof mounted but a gutter rail mount may also work.
Slide extended, awning out to my normal angle. I can drop it lower without the slide causing problems since the slide topper roller tube keeps the awning clear of any corners or sharp edges that could damage the anwing.