Listen up. If your going to find out how to defend yourself from someones fist flying at your face while your playing "Get in my guard," then learn to do it correctly. As I always teach my students, the best way to learn something is to learn both sides or approaches to a technique - offense and defense. So learn the best way to crack your training partners in the face in order to open there guard and keep smashing. (Thus you'll learn how to defend it also)
So lets have Liam of VT1 Gym Sydney shows us how it's done with this great GnP tutorial.