My mother taught us to cut a potato, so we could rub the starch onto the window pane. Three reasons why this is a good method:
You can tell if the window has actually been wiped; there will be white starch if you didn't get it all. It will turn black if you leave it on long enough.
The starch traps in the grime, you don't have to worry about having to clean the sill because all the grime dripped from above.
The starch is friendly to those who have allergies to cleaning fluids because of the scent or of skin irritations.
I have never heard of doing this! Think I'll try it on my patio doors since my cats like to put their noses on the window panes. If it works I'll let you know.