As I said everyone has their own way of doing things.
For basic autos I think you should be aiming for a 60 kt attitude, this helps keep the RPM management much easier. Keep it simple. When the student has got that, then you can move onto autos at different speeds to lengthen/shorten the glide.
The biggest problem I used to see with students is that they would move the cyclic back and forth to "chase" the airspeed, and the RPM would go bonkers, then they would pump the lever to try to control it. Then it becomes 5 times more difficult than it should be.