This may be too late.....but I use a squeegee (sp?). It leaves the windows spot less, I have an all glass front door and after I wash / squeegge it, peaple tend to "walk into it" they don't realize the glass is in the door.
As for the solution, I use something called "squeegee off" I found it years ago and it has lasted because you use about a teaspoon for a gallon of water. I have also used just soap and water. The squeegee is the trick!
Good Luck,
Joyce