Hi Ian,
I found that my multi purpose ladder was not high enough in A frame mode. I use it extended, tape a piece of thick foam around the top to avoid damage and spread the load, lean it against the roof/wall/awning rail joint where it will strongest.
I use an extending pole hose brush (the type that has a built in shampoo container) Halfords do one that uses soap sticks for instance.
Regards
Bill Dawes