Fshguy's solution for the Trick Score Master achievement helped with this.
I had a friend join as a guest. You must have an actual person for this solution to work.2.
I selected Multiplayer and the very first Trick Score course.3.
We both selected basic characters (avatars) and basic boards (the first one). I don't think that the characters or the boards are of any importance.4.
We both jumped from facing right to facing left the whole way down the mountain. I finished 1st and my friend finished 2nd. We didn't even have to try very hard, the AI was way behind.5.
I unlocked this achievement and also "One-Two Finish."
I imagine you could also end up getting either of these achievements (but I'm not 100% since I already had a clean race and didn't run into anyone):Comments and feedback are always welcome! Good Luck!