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Seems like that would take a lot of practice to do it smoothly and confidently not to drop the shell when the adrenaline is pumping (no pun intended).

This is a simple drill. You may drop shells. However, if you do, go to the next one. No one can tell you what can happen in an adrenaline pumping dynamic situation--you might faint and collapse, who knows.
But with firearms, everything takes practice...EVERYTHING!
Practice can never do harm...being unprepared and unskilled most certainly will cause harm.