Good to hear you convinced her to change.
I got asked by someone enquiring today which method I used to clean windows.
When I said I use wfp she told me they already had a window cleaner that used that method and the results were appalling.
She said the rear windows always have run marks because the window cleaner told her the water dries too quickly with the sun on the window.

I politely mentioned that her window cleaner deserves a bo**ocking!
She told me she now wanted her windows cleaned with the Traditional method.