The best and most effectual way is to scrape of the excess using a scraper, but if the solution has been applied for a long time and the weathershield is dried and hard, then you should use a heat gun to remove the weathershield. Getting the weathershield off is only one part of the problem. You also have to wash off the chemicals with water and detergent or in a commercial sprayer. You should use full water pressure and not just a trickle from a hose to get the chemicals out.