Fun video, but one note: You should always use sandpaper as if someone else is paying for it. It gums up faster than you think, and if your "250 grit" sandpaper is full of tiny particles that wore off and is now acting more like 1000 grit, it just means more wasted hours for you. It's fairly cheap stuff, so don't forget to change it often - certainly more often than seen in this video.

This is particularly important at the initial state where you're eroding down to a level - when you're just going through grits smoothing it matters somewhat less.