I was successful interlining from UA to ANA (2 separate tix/PNRs due to an inability to get an award flight for our first positioning flight) CVG - ORD and ORD - NRT. Thank you for all of the help/advice.

Few things I found interesting:
Initially, UA on twitter advised I specifically NOT check-in to either flight beforehand in order to interline. Response/s on here said that doesn't matter. It didn't as I was auto checked-in for the ANA flight and did so manually for UA flight.
As advised, extra time was needed at CVG. And as expected, the first UA employee mentioned, "I'm not sure we can do that." A second employee made it happen w/in ~10min.
As I understood it, since UA was the first carrier, I would be responsible for paying any bag fees even though we were in J on the ANA flight. Unless I misunderstood that, I was surprised that the UA employee did not charge me (forgot? Saw we were in J for the ANA flight?).
Just noticed the comment and not sure if it applies the same, but we didn't "confirm the bag transfer at the transit desk." The bag came off the belt at NRT without issue.
(unrelated- the Polaris lounge at ORD is amazing)