This is what I've gathered from Youtube videos and some experimentation on my own part; You want to drift hard left or right which will whip the kart sideways, the moment this happens the front of the kart will appear to curl toward the back and that's when you want to steer hard in the opposite direction to straighten out again.

With that said, I'm having a hard time making it viable. Practiced a bunch in Time Attack and I wasn't able to get ahead of my ghost which was just starting the race normally using no technique at all. I've found it's really useful for maintaining boost stock without losing much speed on stretches of straight track though.

I have a feeling my initial drift into the technique isn't optimized enough and/or my timing is off. That or I've misunderstood entirely lol. In any case, I need to watch more footage of it happening since most of my research has taught me a little bit about each technique but not a lot of detail for each specific one.