It is a devilish question, one we make each time we develop and certify a helicopter, bugdevheli.
The training has to be automatic for power loss in a single engine helo, with an instinctive connection between the rotor rpm and the collective. There is no decision, no cogniton (thinking) involved if it is to be successful.
Back when I was very wet behind the ears, my instructor covered up the rotor tach and made me fly most of a training session, just to prove how the sound of the engine and the beat of the rotor become part of your subconscious control loop.
If you were to use the 1 second comparison when someone throws a rock at your head, you'd get pranged every time. Ditto with the flame of a hot stove. It not only can be learned, it is the entry point for allowing a solo flight, IMHO!