Excellent Reply Ally
It would be a weekly wash for Hessy - an "all rounder" including arches etc:
I got one of the Aluminum pop up/ down extendable ladder thingy-ma-doodle-job and made a cushion rest from old cushions for placing over the top rung- although resting it against the top sides is fine as long as the awning slit is not touched.
I leave the bucket of soap mix on the ground and use the extendable wash brushes as previously suggested to rub down the roof and tie the hose through the top rung to wash down. You can reach and dunk it to bring soapy water to the roof.
I use 4 points (2 Each side of the unit) so to cover the roof and ensure the crevasses are done along the roof lights etc.
I used the GRP Boat finish lacquer to T-cut and resin coat the roof - 2 coats last summer which was applied and buffed with a lot of luck so not to slide off the roof

as i did it all while lying on my stomach precariously

at points especially when buffed as thought i was going off the roof "like a penguin off an ice berg"
It did nearly a full year now and still retains a good sheen -thank god there is no trees overhead where i park, or telephone/electric lines for birds to aim at hessy as target practice - so that's a good help in keeping it clean.
I'll get a couple of good coats on again this year and also replace the silicon seals around the openings. Does anyone else use Glycerine on their rubber seals?? To keep it spongy? :blink:
I'm glad i don't have the overhanging bed units that you other Criacers may have as i am sure it is so very different to clean in comparison to Hessy's roof - May i suggest a course in rock climbing :whistle: , a hard hat

and watching Mission Impossible a few times