FCE Cloning Effect - Advanced masking - ??

[Jamie Brooklyn]

Hi all,

I'm using FCE 4.0.1 and I'm trying to create the cloning effect (Where one shot of subject A is superimposed over another shot of subject A - both in different positions - so that the final product is TWO subject A's in the same shot).

I know what I need to do to make it work, which is:
Superimpose one clip over the other
Mask out a subject on the top layer leaving the bottom intact
Adjusting the mask so the subjects don't interfer with each other.

Ryan from FilmRiot does it exactly - at 0:58 - this video.

Special Effects: Human Cloning and Camera Techniques - YouTube

I know how to crop a clip, so I can make a very basic cloning effect, but I'd like it to be more advanced.
I've read in a FCE ebook I have that I could use an "eight-point garbage matte" to create something similar, but eight isn't enough points for the detail I want.

I want to be able to go through and frame-by-frame arrange a whole lot of points, so I could have something intricate occur - like subject A walking behind subject A.
In the video link above, one character slaps himself in the face - at 5:11 - which is the type of interaction I'm after.

Any help is much appreciated :)

Thanks