IMO, if you want to shoot 90%+ on 10 pins, learn to roll the ball straight so it rolls over the finger holes. That is how WRW does it and he has the highest spare conversion in history. I used to try to follow the motto "just throw your strike ball but with a plastic ball". Yeah, sure.. that works real great when the ball will hook 2-3 boards. Boom! You just ruined your margin of error by like 20%. I basically, put my thumb in loose and don't shove my fingers in the ball like I would on a strike ball. Then I break my wrist and then forget about bowling. Pretend like you are rolling a ball to a pin. I also think it looks pretty OG when the ball rolls perfectly straight and nails the 10 pin. I got a lot of compliments this past summer league on my spare shooting.