If while training a recruit or acting as an FTO you find that your “student” continues to put things in his gun hand--things like a flashlight or notepad--and your verbal instruction doesn’t seem to be sinking in, you can try this:
Have the officer wear a rubberband on the gun hand wrist and when they’re caught with something in that hand, you can verbally tell them and you can also give the rubberband a pop on the wrist. It won’t take long for the point to sink in!