Jandy, welcome to IRV2
Its good to have you aboard plenty of info here to help you out. Rain-X is a good product to use and there are others. On top of your post the word "FIND" type in "windshield rain" take off the check mark and you will have 70 posts dealing with your problem.
If you could help us to help you in future, post your coach and chassis info in your sign-profile block it will follow you around when ever you post a question or answer one for someone. As a owner of a Newmar coach I can place you as a member of the Newmar Forum nothing you have to do other than to say yes.
Enjoy the forums and be safe.