Wow. Firstly don't EVER scrape anything off of a car, windshield, paint, anything. You didn't tell us what car he has but let's assume it's an M, he can't get a remote starter installed unless it's a shop that specializes in aftermarket so the best thing to do is just go outside 10/15 mins before leaving and blast the heat to the windshield and hit the button for the back windshield. By the time he comes out, flick of the wipers and it'll all be gone while the car is hot too. If it's not an BMW then get a remote start!!!!!!!!!!!!!
Questions on here amaze me sometimes, people rely so much on media and the internet these days to get answers to the simplest and stupid questions. Heck I'm only 20 and know how to work things out on my own quicker than so many people on here.