Phil,
I assume you're talking about cleaning conservatory roofs.
They're hard work, even with a WFP, and each job is different depending on the shape, height, size or pitch of the conservatory roof and the geographical features surrounding it (walls/fences that get in the way etc).
Most of mine I do by standing on a ladder that I've leant against the conservatory. I always use a Rojak ladder stopper too, as it never feels that safe leaning a ladder against a gutter. This is probably not 'best practise' though, and maybe someone could suggest a safer method.
After scrubbing and rinsing with the WFP, I always try to squeegie as much of the water off the roof, using a squeegie on the end of my pole. The pitch of conservatory roofs isn't conducive to letting the pure water run off; it seems to sit there and will deposit any dirt it's absorbed when it dries out.
I hope this helps some!
Oh, don't forget to charge well for it; they're hard work and time consuming to do a good job.