I have used this technique to solve a variety of problems over the years. Sometimes figuring out how to explain complex things can be a roadblock. Sometimes we just need to refine the message to foster better communication. A lot of variations to this exercise exist. This is an example of how I go about completing the one blank page pitch technique.
Grab a blank page. Write the topic that is going to be pitched at the top of it. Start to fill the page with the high level content. Work your way down the page one bullet point at a time. Try to avoid getting into the weeds. This is a pitch. You can have some details, but one page is not enough room for all of the details. After you fill up the page deliver the pitch out loud in less than 5 minutes. Now we get to the hard part of the process. Crumple up the first draft of your pitch. Grab a blank page and start the process again. Think about how you want to refine the pitch. Think about what details really sell the idea. After you fill up the page deliver the pitch out loud in less than 4 minutes. Things might be going really well at this point. Crumbling up that second draft is always a hard thing to do. Grabbing that third piece of blank paper and working on the pitch is a key point in the process. This is the time in the process to move beyond refining ideas to demonstrate mastery through simplicity. Explaining things in simple terms that help people understand them is critical to communicating the pitch. After the page is full start to deliver the pitch in less than 3 minutes. This process can be repeated until a polished 45 second elevator pitch has been completed.