My preferance is to teach setting an attitude for a speed, then finding a corresponding collective setting to maintain the height... In training you always pick a speed that is attainable in level flight without exceeding the maximum power setting. 75kts in R22 for example. The other method of pulling to a maximum cruise power setting whilst the practical method most of us use for everyday flying, can prove confusing as depending on aircraft weight and conditions this can give quite a different airspeed day to day.. When it comes to things like navigation , this can prove confusing for the student in terms of planning who cant work out an accurate speed in advance. Better to have one standard speed even if that is slower than max cruise...
When you start talking about IFR helicopter operations, generally the student is experienced enough to use either method...