At this late point in this thread, may I interject?
The only way I could repeatedly get the symptoms for vortex ring state was, at a suitable height above ground, enter from a downwind deceleration. Determine the wind direction at altitude from cloud shadows, or pre-flight weather info.
Starting at 60 knots or so, use a power setting that is less than the power required to maintain level flight, but decelerate maintaining altitude. Passing through about 20 knots, the first symptoms of low frequency airframe vibrations (or buffeting) appears. As the speed passes less than 10 knots or so, the helicopter will start to settle, and the second symptom appears- uncommanded pitch, roll and yaw oscillations. (i.e. the ontrls aren't being moved and the helicopter is dancing around) The rate of descent at this stage should be 300-500 feet per minute. And the student should be told that this is the furthest point you should go before recovery, except here we may want to see what happens if power is applied to recover, instead of lowering the nose.
If the power is increased, the rate of descent may (and I must emphasize may) increase.
Recovery is made by positively lowering the nose to at least 20° nose down.
Typical height loss is less than 500 feet.
I have never been able to satisfactorily get the symptoms (the buffeting and uncommanded pitch, roll and yaw) when trying to do this entering from into wind.
And if you don't get the symptoms, the student isn't going to be aware of them for later life.