I’m down in Florida. We never really have a problem with windows taking too long to get dirty again.
I use Rain-X windshield washer fuild. -35c rating in the winter months as it is colder than most other cities here in Canada. No soap or other chemicals or solutions work, even methyl hydrate. Rain X major benefit to me is the polymer allows lubrication for my squeegee and it contains methyl hydrate that i need to cut through the dirt. Nothing else in the market is as effective as this. $5/gallon and I use a Gatorade bottle with the twist tip to wet my applicator. So I can make it stretch with no major added costs, and no coat to the client either. Rain X does work quite well I have to say.
