I have never actually tried this trick, but I happened upon it the other day, and there are a lot of iterations of it on YouTube, so there’s probably something to it. This could be useful if we do get the storm that forecasters are expecting this weekend. (I’ll report back after I give it a go. Have you ever tried it?)
The “rubbing alcohol + H2O” will work fine for clearing an icy windshield BUT you should not get any of the solution on any painted surfaces of your car, as it may mar the paint.