Some wag once wrote in HJ section of Telegraph suggesting toothpaste to clean windscreens and I was dumb enough to try it (not with a toothbrush though). HJ's slot has over the years repeated tips for car body wash+wax and favoured (best?) brand, but little or on the most important bit - the windscreen. Household windowlene and green spray glass cleaner cleared the dirt and film inside and out but didn't last or water-repel. Tried Halfords various 'glass cleaners' and then 'glass treatments'. This worked. But applying a rain repellent/treatment is a bit of a faff, espec after cleaning car and glass, or just glass. The Holy Grail is now achieved and a few of the major players now have an easy to use, spray on Glass 'Cleaner + Rain Repellent'. And no, this isn't a marketing slot. Probably all made in same factory but Turtlewax Ice 2in1 is good. But my fave for ease of use is RainX 2in1. Now I wouldn't suggest this on public roads, so a disused airfield is ok, but at speeds of 35/40mph+ rain just beads away leaving clear visibility, you almost don't need wipers. Works on all front, side, rear glass and mirrors. Any hints or tips welcomed. These are about £7 bottle but last ages.