Balancing my film career and my music will be something I'm just going to have to deal with, as it happens. I think I can balance it out; the choices will probably be pretty clear. If there's a movie I just have to do, I will work the music around it.
What convinces is conviction. Believe in the argument you're advancing. If you don't you're as good as dead. The other person will sense that something isn't there, and no chain of reasoning, no matter how logical or elegant or brilliant, will win your case for you.