Hughes 500 - your description of the high speed cruise technique for auto is OK for a practice one where you react immediately so the Nr has little time to decay - in the real case you will need to lower the lever a bit because you will be using the strong flare effect to recover the Nr rather than zoom climb.
We used to teach this type of technique on the Gazelle at low level (100') at 120 kts and you could show a climb of 2-300' if you reacted quickly but that was a false scenario with no delay between closing the throttle and applying aft cyclic.
Try doing it with a 1 - 2 sec delay between throttle chop and reaction - you won't be getting 500'/min RoC but you do recover Nr and delay the onset of the descent giving you the all important time to make a plan.
The other area you have to be careful is when the flare effect is waning and you have a nose-high attitude; you need to select a speed stable attitude for your best auto speed but you must push the nose forward gently - any rapid pitch nose down will decay the Nr you have worked so hard to recover.