This is a great trick! I would try around a 45 degree angle, higher works okay, lower is a little tougher. I just threw a few STMs to see the angle I normally use (which is 45).
I am including a few videos in case they help including how I lost my teeth. Best wishes on Shoot the Moon!
I find it helpful to think of a sort of swinging; like you feel the inertia of the forward pass coming back and you flip your wrist to swing the inertia up. Some yoyos are easier than others to shoot with; helps to start with one that has a smooth, snappy response. Sometimes a little bit of a tighter tension can help also
Start with a 45 degree up throw, as its coming back recognize when the yoyo is about to shoot upward around the bottom of your hand, gently push your hand forward to pull out the string. When it hits the top and responds agin, it will pass back under your hand to shoot forward, as that happens pull your hand gently backwards to pull the string out again. Repeat.
This trick is all about finesse and making sure when the yoyo is shooting under your hand and back out/up, the plane of spin, plane of the string pull, and the gap all need to line up otherwise youll pull the e yoyo off center and wobble/lose spin.
I hope your dentist was more understanding… Mine was a friend. I had to wait until they quite laughing. Then Dr. Tom Kuhn (dentist) heard the story and took photos of my teeth at Nationals. Best wishes with your new tooth. My new teeth have been hanging in there for over 10 years. I just look really scared shooting the moon.