I just got mine today! I found that getting the coin to spin consistently for a long time is easiest with two hands, using the index finger on one hand and the thumb on the other.
I am right handed so I use the thumb on my left hand and middle finger on my right hand. Then I get close to the spin surface and let it rip. The key is to focus on trying to release both fingers from the coin at the same time. I also try to get as much surface area of those two fingers touching the coin for the best grip. That works for me at least.