Ernest Hemingway famously said "The first draft of anything is shit." But he was referring to the art of writing novels. Do you think that's applicable to screenplays? I know many writers that do several rewrites for months before they'll let anyone read their work.
Perhaps you've heard of Irving Ravetch and Harriet Frank Junior? They wrote a few screenplays including Norma Rae, Hud, The Long Hot Summer and Stanley and Iris. Here's what Irving said about rewrites:
"Usually, we'd get about three pages done each day, and those pages are finished pages. We'd polish them as we go, over and over again, doing our revising as we proceed. So when we're finished, we're really finished. We very seldom do any revising.".
I work faster but very much like Irving and Harriet. I do a lot of polishing as I go along. When I complete a first draft, I read through it several times to remove non-value added dialogue, scenes and narrative. If something doesn't move the story forward or bring value one should consider losing it. If you're interested, this is a fairly decent article on what you should do during the rewrite process, much of which I agree with. http://www.scriptmag.com/magazine/the-craft-rewriting-tips-writer-edit-t...