Complex sentence: Among his most important influences came from working with Spencer Tracy and George Cukor in the 1942 movie "Keeper of the Flame", praising their patience and ability to give due attention to inexperienced actors such as himself.
Split into simpler sentences: Among his most important influences came from working with Spencer Tracy and George Cukor in the 1942 movie "Keeper of the Flame". Hickman praised their patience as well as the ability of both men to give due attention to inexperienced actors such as himself.