Do you have a frame without the actor?
If so: try difference matte.
It will more or less succesfully compare the empty frame with the frame with actor.
There is a possibility you still need to fill in some blanks with an extra layer with a mask, but it should get you started.
(I can't tell whether it will work because of the red overlay.)
I actually didn't know there was such a thing as a difference matte. Wouldn't that take a lot of calculation, though, much like the Rotobrush? I'll have to give that a look soon and see how well it works.