Yeah, the important thing is to add a little grain and to treate all footage with the same effect. He has a collection of after effects color correction presets. Once everything is put on an equal playing ground , as far as grain matching, all things digital have their own “grain” if you will, based on the algorithms the programmers use to get a look specific to the device, and matching a certain stylized look , then its not that hard to mix from multiple sources, Its important to shoot it pretty clean and do all of your fancy corrections, looks, and gradients outside of the camera to ensure nothing goes in that you have to fight against to get that matching look. Anyway, who knows, but it looks good and matching.