Hey guys I'm using this cleaner namely FormalHero, or something similar which is very effective towards these rain-x or water-stain. It costs about Rm11 in Giant. It says, apply it on a wet cloth and rub it on the clean windshield, but no it doesn't work this way. Just apply it on a DRY cloth and rub it on. VERY effective. ALL existing stains will be removed after a rinse. Hope this helps.