I've done ok with the jumps, because the game tells you right away what the ideal release point is. And yeah, slowing down is crucial, especially if you want any chance of doing grinds, or if you're on a bumpier part of the mountain. I typically only press up on the LS when I have a clear path to a decent jump, and even then I let go of it well before I hit the ramp so I have time to get myself set for the trick.
Now if I could just teach my brain to stop doing the same tricks over and over, lol.