My problem with the headlights is not fogging, but pitting, my windshields too for the last 30 years or so. I used the 3M headlight restore system last week then applied some Rain-X, it made a HUGE difference in the headlights, even though I could not go deep enough to get all of the pitting. I wish the windshield was that easy, but then I usually plan on a new one every year (I can usually shop around and get a shop to waive my $100 deductible) from larger debris.