Page 1 - Gathering all the parts

The basics behind Superfast shot a fairly simple:
1. You need to shoot the backdrop for the scene totally empty. You will need this to show through all the layers no matter how they are masked.
1a. If your camera supports the ability to lock in the color, you should do it now so that the ambient color of the lighting of the scene remains as consistent as possible throughout all the shots, regardless of where your actor is.
2. Then you need to shoot your actor running at normal speed. In this case, running out, and then back in. If you wanna do the "Jim Carrey" stance, that's up to you. It worked for me.
2a. Be very careful to be sure the camera doesn't move at all!
3. In short, what you'll be doing is taking 30 frames of footage but only showing 3 or 4, then motion blur the heck out of each frame.

The first step is to set everything up in After Effects. The backdrop image doesn't need to be a video clip. In this case, I sent out the first frame of the video as a PSD and used that for the backdrop. You can do it that way, or make sure that you film enough time of the blank room to fill all the time you'll need. Either way, you start by putting the backdrop on the timeline of the main composition. Then place the video of your actor on top.

Go on to page 2: Setting up the IN and OUT points