Give me a moment. I'll edit this comment in some minutes.
The 3 different methods of turning explained in the game manual (which are, frankly, not as usefull as they should):
The quick turn is a more usefull one.
The simplest way of doing a quick turn would be to:
Now, that method implies starting the quick turn pressing both trigger at the same time. There's also the
option of doing it pressing both triggers in quick succession. So, this would be another way of quick turning:
Although, with this second method, you should take care of not sliding before starting the actual quick turn (something that is not a concern with the first method). To avoid this, it's crucial that (like i said right above) you press the first trigger very slightly. Also, you should release it instantly after you press the other trigger + hold the analog stick (to avoid drifting).
Try both methods and choose the one that you're most comfortabe with. That will be the method that you'll use in most cases, but not in all. There's a situation in which is more practical to quick turn in a similar but not exact way: when youre in the middle of a slide, and you want to change it into a quick turn in that same direction!! In this case:
An example of when you'll be doing that: youre sliding to the right (youre holding right + the R trigger) and you realize that youre going to crash, with the left rail, because you aren't turning enough to the right. In this case, you can
quickly and very slightly press and release the L trigger (without releasing the R trigger) to change the slide into a quick turn (so that you turn harder to the right and avoid crashing).