I'm not even sure that I'd look up the word compositing. Rather I'd look up what to do with your 3d app + photoshop. While technically it is compositing, googling comparing will more likely show you after effects, nuke, and other things which are for compositing film... taking the video, motion tracking, masking, color correction/ grading, adding your 3d, green screen, etc.. useful, but not what I'd prescribe to you at this juncture. But if you type blender and photoshop, or zbrush and photoshop. Or finishing your blender in photoshop, etc. You'll get stuff that's useful.
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And by the way, I decided to follow your suggestion about looking for kitbash too. I've found a good kit and will try it on that tv bot that I posted soon. Let's see if I can apply tertiary details nicely to it... .