I hit mine all the time to show where and how they are open.
It isn’t a death blow, if it is to the face, it is a tap on the forehead. I have also used a fist making connection to the jaw line, again not a strike per say, but I simply place my fist along their jaw and keep it their a couple of seconds. I may also use it to push through, turning their head a bit.
For the body it is a little different. I usually will target the ribs or the chest, and use just enough force for them to squirm if it is to the ribs, and a decent little thump if it is to the chest. To the chest, I am not looking for any kind of force or power, but more wanting the nice thud sound effect.
At the same time I show them how to correct their position to reduce the chances of being hit again. It may take a few times, but eventually they get it.
I also encourage them to strike me from time to time exposing my own openings to them (or what would be the openings of a potential attacker).
This does not always fare so well for me, because they have not yet learned to control their power, but so be it.