Window cleaner has vanished off the face of the earth, so I’m going to attempt to do the downstairs ones at least myself. Best way to do it? Water and.......??
As Margo said - soapy water (not too soapy - about the same strength you'd use for doing the dishes) and take off with a decent squeegee.
Don't try one of those cheapo pound one's .... they won't cut it :)
No need for fancy actions, remember us window cleaners have years of experience and make it look easy (I've been a window cleaner for over 20 years). Just squeegee from side to side.
Get yourself a decent squeegee - for the amount you'll use it, it'll last you a lifetime.
That one in the link, is more than adequate.
If you use an inferior one, you'll never manage it.
I sometimes find squeegees belonging to customers lying around ... so I pick them up and try them. No offence, but if I can't clean windows with them, then it's highly unlikely Joe Public can.
Vinegar attack’s the rubber on DG frames. Some say vinegar to clean outside of car windscreens plus the wipers. But vinegar destroys the graphite coating.