kidjete,
I use Ace Mitchell Shur Cushion. It's a special density foam pad, that adjusts to the shape of your thumb.
I found this at my pro shop. Ace Mitchell's web site will not be up until May.
I used to make my own cushion, using mole foam, and bowling tape. It was a real PIA, to duplicate the cushion size. My driller recommended the Shur Cushion.
Hope this helps,
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I like to watch . . . the ball that is.