Marshalling signals to a helicopter on the ground have the same meanings as those to an aeroplane, provided the helicopter has wheels, of course. It is only in the hover, as far as I know, that a helicopter can manoeuvre backwards. Also in the hover, a signal to move sideways means to do so without a turn.
At an airport it is often very difficult to identify the intended landing spot, so marshalling might be required, again for the same reason as for an aeroplane. Even in the hover, the pilot is relatively close to the ground, and taking the hands off the controls to look at airport plates is not really an option.
I remember flying into Liverpool on a number of occasions. (I forget what offence I had committed.) We had one designated helicopter landing spot, but the ground staff insisted we wait for them to turn up and marshal us to it, even when the apron was otherwise empty. Apparently to do otherwise was dangerous. Then they might marshal an aircraft directly behind us, still with our rotors turning, and let passengers disembark. Apparently that was safe.
Away from the airport, marshallers are often used for underslung load operations - depends on the job and the circumstances.
No idea what your project is, of course, but a few words of advice: Away from airports and professional marshallers, practically everybody misinterprets the "Move ahead" signal when dealing with helicopters. They think it means "Come forward", i.e. "Towards me". So, when they are standing facing the starboard side of the helicopter, for example, if they want me to move to the right, towards them, they signal "Move ahead". They then get confused and sometimes very uppity when I obey their signal and move ahead. It takes a bit of thinking about, sometimes.
One more thing: the marshaller must never lose sight of the pilot's eye. If he does, it means the pilot cannot see him, and he's no use to anybody. It often means a fair bit of running about. Good luck.