I've been using Raincoat, yet another brand of water repellent! Seems to do the job, so long as you going at a reasonable speed 30-40mph + Anything less and the water doesn't get blown off. Similarly, it doesn't help i f it not really raining much, but road is wet and there's a lot of spray from other cars etc. Needs recoating quite often (ever week or so), but each sachet in the box has enough for about 3-4 applications.