Don't worry about it and just get on with it. This is how I would do it...
1. Make sure you are doing a good job of using the wfp and you don't leave spots.
2. Just turn up and just make a passing comment that you are using a new system and you've tried it on your own windows and it's brilliant. Tell them you are using it because you are worried for your own safety and don't want to use ladders any more.
3. Get on and clean.
4. This is the good bit.
Dry the front door and surround
Dry the underneath of the top openers so they don't drip onto the main window below. (obviously only on the ground floor windows)
Wipe the sills and the underneath of the lower windows (basically try to lessen anything that looks like it's dripping).
This should take an extra 3 mins in total.
Find a window that is already drying (I would start cleaning whichever side the sun is at) and show the custy (that although the window isn't fully dry) where it is drying, it is lovely and clean with no marks.
Tell them that the rest of the windows should dry like that.
Plus, by using the brush you have managed to get into all the little knooks and crannies of their window frames that your fingers can't get to.
I use this all the time on awkward new cleans and never lost a single one.
Hope it works for you.
PS ignore the letter, most people couldn't give a t00ss!
