I found that one way to get a student to relax in a spin was to do some 5 - 6 turn spins with them tasked with another task like counting the rotations out aloud and perhaps verbal height checks every 500'.
This act of performing a mundane repetitive task in a high stress situation would rapidly lead to a de-stresing of the situation. After a few sessions they could enter, maintain and exit their own spins without a bead of sweat.
After all - the actual control actions are simple.
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