The two shots are locked off, and identical with the exception of the card, (and possibly a tiny bit of reflective spill from the card which should be easy to mask out). They were shot with a DSLR so they are very high quality and noise shouldn’t be a problem.
I am unfamiliar with mocha.
If you were to use another method to make the mask what would you choose? The foreground trees are very fiddly with lots of twigs and leaves, so painting a mask would be a pain, and is compounded by the fact that the final product will be in stereo 3D, so I would need to be able to make a second mask that paints out the exact same elements from a slightly different angle or the 3D will cause headaches in the viewer.