From the video....the black paint came in ONE gallon cans?!?!?!?!
Underfire, I don't have any experience with aviation paint, but I do have with automotive paint which I believe is similar (I've painted a few cars). The
color comes in one gallon cans (or smaller), but you mix it with a whole bunch of stuff before you spray. So one gallon of color makes ~2-3 gallons of sprayable paint. Once you add the catalyst, you have maybe 30 minutes pot life, so mixing more than a couple gallons at a time just invites waste (and the stuff is expensive - automotive is a couple hundred USD/gallon, I'm sure the stuff Boeing uses is several times that - so you don't want to be throwing it out...).
BTW, I doubt the painters like black much either. Very unforgiving to use.