I'm one of Justin's filmmaker friends.
Good stuff. The thing that strikes me is when you mention how there's so many actors all crammed into the frame at once and many times they're blocked from view, but the staging is so well done that we see things at the right time. I face a similar issue as a re-recording mixer. Many times in a shot or sequence of shots there are several sound elements all happening at the same time. Several actors are talking over each other and maybe there's some movement or action that grabs the audience's attention but ultimately a line of dialog is the primary focus of the moment (or the director thinks it is). I try to mix the soundtrack just like good staging; to get the audience to pay attention to certain things at the right moments while still giving them the impression of hearing everything at once. It's very easy when the blocking, camera work, lighting, acting, and then editing all contribute to setting that up. It's a real struggle when they don't, or are doing things that are unknowingly drawing the audience's attention away from what's important. And many times filmmakers aren't aware that it's not working until they get to the sound mix and the realization sets in that they can't hear the important line of dialog at the same time that the truck is crashing into the wall. What looked visually dynamic is now a mess of clashing visual and audio ideas. As with all good filmmaking it's amazing to see such a complicated scene as the one above put together so masterfully that ultimately it just seems so simple, or real.