what i use to clean con roofs is :
small telescopic ladder, for con roofs with limited access, so you can get to the roof edge, instead of standing back .
i use a designated pole and brush, i like a flocked brush with fans.
garden sprayer, with 5mtrs of hose, inline tap and pro end stop, into which i plug a converted harris pole with a nozzle at the end to pre-treat the con roof of gutter/fascia etc.
hope this makes sence.