not really, I don't really like them, what I would do instead is really show them how to clean on a first clean.
what I would do, is before using your preferred method of first clean, scrub the sill like five to ten times across the length , turn the water off, do it again, and then scrub backwards and forwards across the length of the sill clean the windows, (the green bits they have left will be soaking in now) and then go over the sill a couple more times at the end ---- show them this method and they will be fine, I know you wouldn't need showing but with the over exaggerated demonstation you will install good habbits, imo there are so much nicer brushes to work with than sill brushes