How to switch from read-only slave to read-write after Postgres Master Failure?

Hi, I was wondering how easy is to convert the read-only slave to read-write while the Master is down. There is a tutorial here that provides a step-by-step procedure on how to streamline a replication process. However, it does not provide info on what to do after the Master goes down for a reason.

And I also had a tough time locating something relevant on the internet.

An help, url, suggestion will be kindly welcomed.