I use Mother's Carnauba Cleaner Wax on my bike and my windshield. The carnauba oil in the wax is very good for the plastic and the wax protects it. With a good coat of wax on the shield all you have to do to clean off bugs, etc. is to soak the bugs, dirt, etc. with a wet wash rag until it easily wipes off. Then, dry with a clean soft towel. The extremely mild cleaner abrasive helps keep off fine scratches. Once you have it waxed, don't use regular windshield cleaners as they will remove the wax. Just water or mild soap and water is all you will ever need.
