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?