The best advice I can think of is:
a TRUELY free arm swing all the way from start to finish. and during the finish POST your shot... which means that when you release the ball you should be balanced and able to hold your same position when you let go of the ball. (it helps to have good timing and a good fit on your ball first but I cant help you there)
I dont know if you would call that a "drill" but its what I work on every single shot during practice.
I dont want to say anymore as im not a coach
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tweener
high track with medium revs
medium speed
specs and ball layouts in profile
currently throwing
Visionary (O.P. / O. SS.)
Rotogrip (rogue cell)
lanemasters (black pearl)