Guys bascically to recover from a low g situation where the heli has rolled right eg : R22, R44.
Either aft cylic to reload the disc or the best way is to lower the collective.
The only reason why the heli is rolling is because the main rotor has become unloaded and for the given power setting the tail rotor thrust causes a the heli to roll.
The easiest way to understand this is enter a autorotation quite quickly and you will get weightless eg: low g. The heli will not roll as there is no torque being produced so the tail rotor will not roll the heli.
All the way in a auto and in the R22 below 18" you can and push and pull the cylic and the heli will not roll because the tail rotor is not producing enough thrust to roll the heli.
I find teaching lowering the collective the easiest way to advoid mast bumpig to a student. As in the mountains approaching a pass simulating bad weather you usually have alot of power in use and if they bring their speed back to 20-30kts this is not enough airspeed to relaod the disc if they nose the heli over adburtly so lowering the colective is the safest.