The windows in our house usually need to be cleaned on the outside in the spring and fall. We have a big willow tree right outside our front door, and it gets very dusty. Then it rains, and all that dirty dust gets blown onto our windows! Yuck! I found this recipe for window cleaner in the Halifax 1st Ward 2008 cookbook.
2-3 tablespoons laundry or dish detergent
1 tablespoon dishwasher wetting agent (e.g., Jet Dry)
1 gallon warm water
Brush or sponge on window, immediately hose off. Water will sheet off, no drying necessary.
I have used this, and it works! I use a squeegee with a sponge on one side, with an extension arm.