The biggest factor affecting my revs and total hook is the fit of the ball. The quickest way to screw up a good release is to have a thumb hole too loose or too tight. It is nearly impossible to be consistant if you have to knuckle the ball to keep it on your hand long enough to get to the foul line. The amount of pitch on the thumb also makes a big difference on the revs. The more reverse pitch the harder for me to get as many revs. If the span is too long it limits the revs. If the span is too short it seems to cause a lot of inconsistancy even though the revs are higher, which combines for a miserable time trying to adjust when almost every shot is different.
To add more side turn, I position my hand so I'm as far underneath the ball as possible on the approach and keep the palm open, facing away from the body, as long as I comfortably can on the swing. When the ball is passing my ankle on the slide is when I start to rotate around the ball to finish with a thumb pointing straight up if everything goes well. This will add more spin/side-turn to the ball, delaying the hook and covering more boards farther down the lane. Sometimes this works great, like on a blocked shot with dry outsides and shorter oil. But on a more demanding condition this is trouble waiting to happen. Then side turn is a curse for me and I try to stay behind the ball as long as possible and come up the back.
I also use urethane thumb slugs. For me the reactive resin or particle ball covers are tough to release even when they fit right. The slug just is easier to fine tune and gives me a cleaner release. If you aren't using one maybe it is something to think about. Hope this helps you out.
