I would suggest, washing the windscreen and wiper blades as normal using car shampoo, hose down, then clay the glass thoroughly and, re-wash. Dress with AG Glass Polish, although I must warn, that I find with a screen with chips the polish sticks in the small cracks. Also wipe the blades with the polish allow to cure and buff off. Alternatively, and what I currently use and really like, is Auto Finesse Crystal and do the same. Watch the rain speed off the screen like it is coated in silicone.