That is not a problem. Follow the directions and you will be fine! Clean the windshield with glass cleaner. Then apply it lightly in circular motion. Once it hazes wipe it off with a damp lent free cloth. Then take a dry clothe and buff it out. I would repeat as i find that two coats works great! If you do it properly you should not have any streaks,smears or cloudiness. The most you should ever have to do is hit is with damp cloth and then buff it with a dry cloth.
I have been useing Rain-X since the early 1980's when it first came to market. My Dad taught me to use it as a kid. Most people fail to clean their windshield first or put too much on. Rain-X is Acitated Alchol. All alchol sold for health,hygine or commerical use is denatured reguardless of color. The green alchol at the pharmacy has mint,wintergreen, or eculyptus(sp) oil in it as a general lintament(sp).
Now I will warn you about never fog though! I do not care how well you apply it it always leaves a smudged look on the glass when headlights hit it at night time!