A mix of hydrogen peroxide, rubbing alcohol and water to remove bugs and dirt from the windshield. Guys that ride motorcycles use this trick to get the bugs off the windscreens and plastic fairings. The bugs just slid off afterwards. Also my local FBO uses "helicopter polish" it has a waxy layer after its put on but drys clear and lasts a while. I get a free windscreen cleaning while they put gas in the plane. well free is not the best word because they do charge 15 cents extra for full service, being the truck comes to me, air oil etc.