Once upon a time most screenwriters used typewriters to write scripts. Though some still do, I would venture to guess that most screenplays are written on a computer these days. So a word of warning—the wite out test isn’t advisable on computers except in a metaphorical sense. Wite out being the white liquid that was once a daily used commodity in offices everywhere, where if you made an error on the page you would apply wite out over the words you wanted to omit. Once that dried quickly you could type over it. Sure it wasn’t pretty, but it was effective and saved you from having to retype the whole page.
“You know, the idea of individual voices, that’s a toughest thing for a screenwriter. It’s always been the toughest thing for me. The first draft of a lot of scripts that I put down and say, ‘Okay, I’m not going to make that into a film’ is that everybody sounds like a version of me. And a great test that somebody told me to do early on was, ‘Take your screenplay and wite out or cover-up the names of the characters and then read the scenes. And can you tell who’s speaking based on the tone of their voice?’ Is their dialogue distinct enough that you can identify them from the other characters?”
Filmmaker Edward Burns (The Fitzgerald Christmas)
The Q&A with Jeff Goldsmith
P.S. Jeff Goldsmith, formerly of Creative Screenwriting magazine now as a digital magazine called Backstory; The Art and Business of Storytelling.