I love Rain-X. can't live without it. I was replacing wiper blades because I thought the wipers were doing a crap job wiping water.(i use expensive Bosch). All along it was a nasty Film on my window, i used everything possible just to get the film off .. then I used Rain-x and Now i can see 110% better in the rain. thanks rain-x!
The best way that I have found to use Rain-X is to clean the windshiels first with soap and water and then dry the windshield. Then apply Rain-X on the windshield and let it sit there while you wash the wheels/tires, wheel wells and any other trim prior to the main vehicle washing... Then procede to wash the rest of the vehicle. The amount of Rain-X that is being washed of during this time is minute IMHO. The towel/shammy drying process will leave the glass looking great and will not leave any streaks/smears on the windshield. I do it this way about every 2-3 week depending on how much rain we are getting or extra car washing that I'am doing. I also try never to get Rain-X directly on my wipers while Im applying it to the windshield, as it tends to dry rubber and make the wipers hard and chattery during colder months.