It absolutely helped - to write the father in both 'Juicy' and 'Beasts ' I had to see the whole story from his point of view. All of a sudden I understood more of what my own father must be going through - the fear the frustration the anger... the hope that he'll leave a legacy.
Anytime you cast a movie and you need someone famous in the lead part you're a prisoner of whoever happens to be famous in the six-month window in which you're trying to get a film financed.