Sure thing, happy to help. 3 of my chromecasts got taken out with the bad update and I spent a bit of time this afternoon using that method I posted to get back just fine. Root's gone but I don't need it anymore.
The build it came back out with was 220XX... can't remember the XX and, even though I think it's right, the 0 is questionable too. But I know for sure it was 22-something. But that's an unpatched build so the second Google updates your chromecast with that build it will roll you up and shut the door on root forever.
If it was a version before 16x it might have been possible to root newer CCasts by flashing this older version but not going to happen. Unless it requires root to flash in the first place...Anyway just a passing thought.
Just to be clear...You really only had to reformat the jump drive on the first unit, you probably could skip all that on the 2nd and 3rd and go straight to plugging into the next unit with the powered OTG and letting it flash.
Or am I mistaken on that?