I claybar right before I buff my car for 10 hours. I claybar my windshield after every clean before I rinse and seal it. Makes rain bead and fall right off. My windshield wipers are almost never used because I have perfect vision in rainy conditions. You can also physically feel a smoother clear coat after a wash and claybar. Hope that helps. If you want a better than factory new look to your car you gotta wash, claybar, buff, wax and seal your car twice a year.