How to prove to yourself that you squeeze.
Cut one long piece of tape about the length of the thumbhole. Starting about 2/3 of the way down, 
cut a shorter piece. Lay shorter pieces on until it fits what's missing from your thumb. 
from the bottom up until you have a wedge about the shape of the bottom of your thumb. 
Lay one piece over the whole length and insert into the ball , making sure it's far enough  
down to get your whole thumb in. It should hold your thumb straight. Try some releases
in practice. If you squeeze…you'll feel it. Once you've felt yourself squeezing you'll start
    to keep your thumb straight on your own and can remove the tape wedge.
Base piece 1
Top piece
Piece 2
Piece 3
Piece 4
Piece 5
Piece 6