The friend in question appears to think that his inverted track leads to too much hook. He has to use a lot of less flaring, less aggressive equipment to match up. He is an older gentlemen, so perhaps it is his ball speed that is more in question here.
I just thought perhaps it could be explained better. For example, thumb passed fingers at release, rather than a spinner where the fingers are far behind the thumb at release.
He has bowled for quite a while, and has tried in practice to change his track, but doesn't seem to be able to.
He does put his thumb in the ball to answer one of your questions. It also appears that he kind of rolls the ball off his palm, rather than rotating around the ball as much as some.
It is nice that others can change their tracks, and I appreciate that talent, but my question was how to teach that, or show that to someone else?
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dR3w
"Some people are like slinkies, not really good for anything, but they bring a smile to your face when pushed down the stairs."