Karl Townsend wrote:
... On my Dewalt, I don't see how I'd hold the drill
from turning to break the chuck loose - how'd you do that? ...

Chuck up a hefty hex key, 1/4" say, with the short arm in the chuck.
Give the long arm a whack with a hammer. The inertia of the drill will
hold it long enough to loosen the chuck. Works a treat!

Bob