This is a great page on hooking OR to Booking.com: https://www.ownerrez.com/support/articles/connect-ownerrez-t-booking-com
Is it outdated by the new channel manager? Is there a similar page for ABB, HA/VRBO, Flipkey?
(Yea I know, I havent done these yet - trying to understand - I am focused on descriptions, legal agreement, getting the places ready)
Yes, that's the guide for connecting Booking.com. It should be up to date though, frankly, you never know with Booking.com. The screenshots may be a little stale in places. Their UI changes almost weekly it seems.
HomeAway and TripAdvisor need the same guides. We've cut images and done some work on it but just haven't gotten it together yet.
We made this one in collaboration with the HomeAway team, so their integration specialists will give it to you if you ask: