I don't know the answer to this, but Ferrett Steinmetz does, and in his post, 'How I got from First to Final Draft on 'Sauerkraut Station,' he explains the process. Including a link to his first draft with sixty-plus annotations about the changes he made on his 17K word story. And he's happy to answer questions. What a generous offer
Now every writer's different, but isn't it fascinating to take a peep at such a successful writer's process?
*The Nebulas being the annual awards of the Science Fiction Writers of America Association, a very prestigious award.