Now, I'm not a guru, but it's all practice. Knowing that if you smash a kart into the barrier it's a giggle is very different inside your head to the thought of smashing a car. Also, it's very counter intuitive letting go of the steering wheel and watching it spin. 3m7s is good here to see the wheel spin.
Throughout this video you can see Bizz, Steve and I all let go of the wheel completely and then grab it again to keep the slide at the right point. Drifting a Z is awesome fun and they're great cars to learn in, would highly recommend it to anyone, especially if you have someone sat next to you who can help you with learning the ropes.
edit: can't embed the video for some reason :S
edited edit: yay I did it!