A wordspill is when you write without knowing exactly what you're writing.
To write a wordspill, the writer would open up Word, Notepad, or any other text editor, as long as it's capable of changing the text colour. Make the colour white, so you can't read what you're writing. Write nonstop for ten minutes, without highlighting the text, and/or changing it back to another colour. Once you're done, review what you've written, and correct any spelling/grammar errors. Try not to change the text too much, because that would be besides the point of creating a wordspill.
Girl A: Dude, I've got really bad writer's block. I can't think of anything to write.
Girl B: Oh, no worries... You should try a wordspill.
Girl A: That's a great idea! Thanks! :)