Totally agree with above comment, stick with it, they get easier.
You'll soon learn where to start and which direction to work to avoid getting soaked!
Definitely invest in a Pump up garden spray for TFR treatment, so much easier and dirt comes off so much faster.
Best tip, if you use TFR don't waste your 'Pure Water' on UPVC, connect your hose or just your brush thru Customers garden hose, and use Customers outside tap and water supply. tap water works fine.
Give the customer notice that you will need a supply (if they have one outside) that way they will be happy for you to use their water and save your own, just put the emphasis on the Magic of the 'Specialist Cleaning Agent' you use (TFR).
Then finish off on windows with 'Pure' job done and you still have a full tank for rest of days work!
PS ......Also invest is some eye protection, clear glasses or the like, TFR is not good when dripping into your Eyes, I never do a job without mine, supplied by a factory worker mate of mine.
http://www.ebay.co.uk/itm/Clear-Safety-Glasses-Goggles-Specs-Laboratory-/110362183076?pt=UK_BOI_ProtectiveGear_RL&hash=item19b21945a4Good luck
Goochie