Part-way through editing.



There is an feature in after effects which can be used to do something similar. The computer version is far quicker and you can walk away and leave the computer to it, but you end up with a fairly shiny looking mechanical version.
Of course going through by hand and lining it up frame-by-frame is better. Tedious and soul-destroying, but better. I think you can see that it has been done by hand rather than getting a computer to do it.

Computerised motion-tracking with a few seconds of the original footage at the end.