How do you go about transferring accounts/assets after a sale?

I'm hoping to sell off some side projects soon but the one thing that's holding me back is transferring all of the associated accounts and assets after the sale. I'm wondering if anyone has any experience with this. For example with one side project I created a gmail accounts and then registered all third party accounts under that email address so that'd make it easier to transfer them, but they all still have my billing and personal details listed. Should I just scrub as much data as it would allow and then send the login info and tell the new owner to fill out the info quickly? It seems like some services like Mongo Atlas and Digital Ocean don't let you remove billing, I'm afraid someone (for whatever reason) may run up the bill all of a sudden and I'd be stuck with it.

If it matters, the services I'd need to transfer are:
Stripe, Mongo Atlas, Digital Ocean, Vercel, Gmail, Mailgun, and a Github repo.