I'm not too worried about publishing rights on this one. It's a screenplay.

The primary need for copyright with a screenplay is to be sure someone doesn't steal your work. So, I will make sure I file for and enforce copyright on anything I might publish on the blog. But publication rights aren't really an issue with screenplays, except when someone is publishing a book of the screenplay, and then they usually use the shooting script. Which is generally owned by the production company.

Actually, most beginning screenwriters don't even file their copyright paperwork. They rely on the WGA registration service/process. Not the preferred thing to do, in my mind. When I complete a screenplay, I will go ahead and copyright it before I shop it around.

Simultaneous creation is a huge deal in screenplays. Only a registered copyright really proves first creation in a court, and there are enough unscrupulous producers, few though they may be, that screenwriters really need to be able to prove creation date. The old mailed in a sealed envelope trick doesn't work for screenwriters. And while some courts will accept WGA registration, there is an increased burden on the screenwriter when they use WGA instead of registering a copyright.

The business of screenwriting winds up being quite a bit different from the business practices of prose and poetry authors, because the screenplay isn't the end product. It's the outline for the end product.