I have been doing what a lot of people refer to as detailing on cars for over 45 years. There are a lot of great products for glass including ceramic coating and I dont mean just a spray.. But for everyone that is going to experience any kind of precipitation the best and easiest thing to put on your exterior glass is RAIN-X. Just fold up a paper towel and spray the RAIN-X on the glass and the paper towel and wipe all over. If the weatherman says freezing precip do it before . If you put it on and need to drive follow directions and go over the extra residue with a wet towel. And use RAIN-X windshield washer fluid. Glass is fascinating as it is amorphous solid which means it not really a liquid or a solid. Try telling that to someone that gets hit in the head with a bottle.. So if you really have time you can scrub the glass with Bon-Ami to clean it and then apply.. DO NOT use any other scrubbing powder as you will scratch the glass. Or for those of you that are familiar with clay bar that cleans glass well too. And the more often you apply the better and longer it lasts. Hope this advice helps and no I am not a Rain-X salesman just a long time user.