Here's how to fix it.
How would you clean the windshield after an improper application
Park in the shade and let the glass cool.
Rinse the outside of the windshield with clean water to remove dust and grit.
Wash it with warm water and a small amount of dish soap or automotive glass cleaner. Use a clean microfiber towel or a dedicated glass-cleaning towel.
Rinse thoroughly, then dry with a separate, dry microfiber towel. Wipe in straight, overlapping passes rather than circular motions.
If the haze remains, use a stronger glass-cleaning step:
Apply a small amount of automotive glass polish or a mild 50/50 mixture of white vinegar and water to the exterior glass.
Work it over the windshield with a clean microfiber cloth.
Rinse completely and dry.
Clean the wiper blades with glass cleaner or diluted rubbing alcohol on a cloth. If they still smear, replace them—the residue may have transferred onto the rubber.
Test the windshield with water. If water beads unevenly or the haze persists, repeat the cleaning once. Don’t apply more Rain-X until the glass is completely clear.
Avoid abrasive household powders, razor blades, ammonia-based cleaners around tinted film, and mixing cleaning chemicals. If visibility is still impaired—especially at night—don’t drive until the windshield is clear. Rain-X’s application guidance emphasizes wiping the product off thoroughly; its product line also includes dedicated automotive glass cleaners.
rainx.com