Martin,
Your biggest obstacle will be the one in your own mind. You'll be thinking, 'My customers won't like this', or, 'Maybe it isn't as good as trad', or, 'My customers will think I'm ripping them off', or some other stuff along these lines.
And you may have the odd customer who really won't like it, but it'll be the odd one, and the vast majority of customers will be fine. They just want their windows cleaned. And if any get 'funny', then just tell them how it works and explain you're happy to wait till the customer has checked their windows and are happy with the result before you get paid.
Now, I don't even explain to a new customer how I clean the windows unless I want to use it for a selling point, such as 'I can clean those windows above your conservatory'; I just crack on and do it.
And before you use your new system, which-ever it'll be, take the time to practise first.