I have heard it now a couple of times on the ESPN PBA Sunday telecasts. Randy Pedersen repeated the difference between amateurs and pro bowlers; amateurs work the outside of the ball and pros work the inside. What is he talking about? Usually, explanations for the show are "dumbed down" for the non-avid bowler. Here, Randy steps into it by introducing a concept that needs to be further developed. All he mentions is that the amateur comes around the outside of the ball producing more spin. However, no explanation is given for how a pro works the inside of the ball. At least, not one that I can discern and try to duplicate.
Well, I heard this concept again. Discovery Channel's Time Warp program on December 10 featured Michael Fagan. The show slowed down the footage of Fagan's release as well as ball rotation and pin action. The purpose of the show is to explain the science and physics of everyday activities or events. Michael's explanation starts at around 2:07 of the video. He tries to keep his hand on the inside of the ball and rotate to underneath the ball. By contrast, I'm guessing that us amateurs start with our hands underneath the ball and rotate the ball around the outside of it.
There may be good practice tips in that video. However, I cannot and am not encouraging anyone to duplicate Michael Fagan's style.