@DigModiFicaTion so impressive the amount of fine work you're putting in there. I just don't have the patience for frame painting.
With regards to taking a character from one scene into another, the lighting conditions will be totally different. The amount of work to change the lighting conditions on your character is just mind boggling to say the least. You could get a crude effect using light painting if the clip is very brief, if you understand how light behaves, and not much movement... yes it's possible to take it more complex, but of course, the more of a character you show, and the longer the clip and the greater the movement, it multiplies the work you need to do exponentially and requires an insanely good understanding of light and form.
here is an example of a simple bit of lighting I did, but this was mostly static and it was a small section of his face.
this is the light that I painted.
This was asingle light source,his eyes and that light source didn't change relative to his face, so I could simply track this image with his face's movement.
If you don't have any method of matching the light conditions, the person will look incredibly out of place and will break immersion for the viewer.