Movies are always in a state of locomotion. You start with a general idea of how it should feel and then you find you've got a runaway train. You have to race to catch up: the movie is telling you what it wants to become, and when that happens there's no greater feeling.
I do not know myself how I paint it. I sit down with a white board before the spot that strikes me. I look at what is before my eyes, and say to myself, that white board must become something.