Ask HN: Transfer app between developer accounts on PlayStore

I am an indie app developer, and recently, I received a pitch from a local dev shop to buy one of my Android apps. Now I haven't sold an app before, and the thing is that I have single account from which I've released multiple apps. I need to remove this app, and associated services from my account and move them to the other guy.

I found a page (https://support.google.com/googleplay/android-developer/answer/6230247?hl=en) on Google support which talks about transferring apps between developer accounts, but I am looking for information on what all things I should additionally take care of, and how much time does it usually take for the actual transfer to happen. All help appreciated.