the Donald trump video involves some techniques that could be described as "Compositing" which is combining images,
generally to make it look that they are seamlessly embedded into one another.
in this specific example you would have to cut donald's face - this process is called "Rotoscoping"
then you would have to stick it to the moving face of the original faces - this process is called "Tracking"
and after that you would have to match the colors - this process is called "Color Correction"
to mask a patched element behind another is also "Rotoscoping".
these are all techniques that require practice and dedication and not like common "How To" Tutorial
that show a trick or two (make fire, smoke, other fx) through a recipe.
I would recommend taking Mark Christiansen's Compositing Courses on Lynda.
Thanks for the fast reply! I'll check it out.
Thank you very much for the reply! Very helpful and in-depth. I have an After Effects course by a guy called Phil Ebiner (Adobe After Effects: The Complete Guide to After Effects | Udemy ) Do you reckon this might help as well?