There's no way that the process they taped is the same process used at the scene of the crime. Roller vs. stencil(s), for starters. I genuinely suspect that Banksy (which is probably a collective, let's not kid ourselves) has used a neural network to train the video's spoken sentences on Bob's extensive audio library. It just seems like something they'd/he'd do. No other paint-related comments
I gotta wonder about how he gets this stuff done. That took him, what?, an hour to paint? On the wall of a JAIL. On a busy 4-lane road? Is there a fake road crew working and blocking the road? Creating a distraction so people don't notice Banksy painting on the wall? There HAS to be more to his work than what we see... the planning and execution are the things that really interest me about his work...
I liked that film. Actually saw it in an art-house theater, appropriately enough! But it didn't really go into operational detail (of course) and only talked about how he'd done things historically... when he and his style were less famous. Nowadays, his style is so iconic that a passerby would recognize it, know who was doing the work, and stream it to the internet. I just gotta think it is even harder today to do what he does... and will only get harder over time.
Just off the top of my head, Tabby is identical, but lower quality. Shepard Fairey has the same schtick. LA was chockablock of "Wish I wuz Banksy" graffiti artists; the difference between "that's obviously a Banksy" and "that's some choad painting on a wall who thinks he's Banksy" isn't drive-by-at-night discernible. Didn't he do a schtick where he propped up an easel in a park and painted people's portraits for an afternoon without anyone catching on?