First and foremost, the glass must be clean, then as directed apply to a light haze, then when dried splash water on surface of glass and wipe using some major elbow grease, then buff with a paper towel or clean cloth. This must be done at a warm tempeture! not cold and damp. A heated garage etc is best for cold weather application.
I've used it for years and is a good product.

My trucker friend said: Don't waste your money He uses "Coke" (as in Coca Cola)

I use Ran-X and it works great

I do it two different ways. The first way is: I apply it before washing my car and then let the hose run on the windsheild for a couple of minutes. Then after washing the car go back and dry it with a shamy. The other way is after I wash the car I apply it and smear it over the windsheild. Then I use a orbital buffer to "polish" the window with a foam pad. The last one works the best for me.