I’m late to this discussion - and had not heard of twisting
before, since I’m still a beginner - but after attaching a post,
what I’ve been doing to work harden it, is positioning the earring
up against a steel block so that just the post is resting flat
against the block.
I then gently tap the post with a very light hammer, such as a
rivot hammer, and slowing turn the earring w/post while gently
tapping a few times around and along the length of the post. I
follow the same “work hardening” procedure for longer ear wires -
after tapping, I bend them into position.