I write screenplays. Two are adaptations of my published novellas, and have won honorable mention. Currently, I'm waiting to hear back from three contests and also waiting for the laurels for another film festival that two of my screenplays were accepted in.
So while getting ready to work on revisions of my paranormal suspense novella, Hell on Earth, I decided to write the screenplay version. Why? After all, the novella hasn't been contracted for publication, and if the Hell on Earth screenplay managed to get an option, that would make the work previously published in a publisher's eyes. No, the screenplay will remain on my hard drive with fingers crossed a publisher will offer me a contract.
One thing I did notice was in writing the screenplay, I was also revising the story. For example, dialogue. I would start writing the dialogue for the screenplay, then realize that what the character said made no sense. And I would note this on the manuscript. Or I would be forced to look at a scene I'd written and realize I'd had the wrong location. (I've since remedied that by using Scrivener to keep track of scenes.)
It's not a full-proof plan, and obviously won't work for everyone or for every book. I think what happened was writing the screenplay adaptation put my mind in a different mode, gave me a similar but different perspective.
At least writing the screenplay was a lot more fun than going through the manuscript and finding those "garbage" words.