Rain repellents create a protective armour over the glass of your windshield, allowing the rain to run naturally away instead of being erased scratchily by the wipers.
How to keep my windshield clean after applying Rain-x - Quora
Rain-X Original Glass Water Repellent 103ml - 800002242 - Rain-X
What is Nano Coating? Is it Really Important?
Cosway AutoMax Rain Repellent
The benefits of using rain repellent on your windscreen this winter – Automotive Blog
What are the advantages of using rain repellent? - BD Clean
Rain Repellent - EnduroShield for car wash and detailing - lasts 1 year
Southern Wave Express Car Wash
Protectosil® CHEM-TRETE® PB VOC - Evonik Industries
Meguiar's Ultimate Glass Cleaner & Water Repellent - Premium Glass and Window Cleaner for Quick Cleaning with Hydrophobic Technology that Acts as a Rain Repellent Improving Visibility in Rain, 16oz