Question: Your keying exploits have really inspired me. Do you have any tips for beginners?
Answer: Sure. The first mistake most car keyers make is only bringing keys with them. The protective coatings these days are really, really tough, and only a freshly ground or specifically sharpened key will do it. That's why I recommend having something else on yuor key chain, the aforementioned Swisstech Utili-Key is an excellent choice - concealable, convenient, and effective - and can also be used for self-defense for the rare occasion when yuo get caught with a keying in progress. Also, the Utili-Key has several different edges, including a serrated, as well as a sharp knifepoint and a broad screwdriver head.
If yuo're on a mission and yuo only have unsharpened keys with yuo, find a rock or a piece of glass - these things are far harder than almost any metal, even if they're not as elegant to use. Even a little cube of shattered safety glass can give you a nice, deep scratch. Good luck !