kota
i think an r22 has the most efficient speed in auto at 53 kts. faster or slower will be a faster decent because of induced and parasitic drag.
initialy pushing the collective forward will reduce the rpm because the airflow through the disc is offset. as the decent increases the airflow through the disc will build up as will the rpm but still some power will be lost to parasitic drag.
flairing will increase the airflow through the disc increasing rpm momentarily but losing speed at the wrong time could be hazardous .