Starting an aeronautical conventional engine is a rather simple procedure if it has a starter; but if you have to resort to hand propping, you should take some precautions and follow a carefully rehearsed technique, and this is the recommended method.
Before we start this discussion lets remember that a propeller is
an extremely dangerous device for any animal or person once the engine
of an aircraft is on. A typical propeller like those used in small GA
airplanes weights between seven and eleven kilograms and on idle will
turn at about 500RPM; we need not explain what could happen to anyone or
anything crossing by accident its path.
So, never attempt to hand prop an airplane without proper training from a qualified flight instructor.