after a bit of experimenting... the correct way to do it is...
start your Pose,
then in the PWS, in the temporary Action that is created while Pose window is open,
enable Show more than drivers to expose the "Bones" folder
each bone has an eye icon that can be set on or off to set the bone's "Hidden" property in the Pose
This allows you to explicitly set a bone to Hidden OFF which was hard to do with the J key method.