Start off by saying that the goal of the post-mortem is not too blame anyone or point fingers but to find out where improvements can be made and where downtime

Start off by saying that the goal of the post-mortem is not too blame anyone or point fingers but to find out where improvements can be made and where downtime and incidents can be reduced. Every time a team is paged at our company we have a post-mortem meeting to review the incident. If we have a lot in a specific week we do them in batches when possible. We pull in anyone involved with identifying, triaging, or resolving the incident and create follow-up tasks based on the meeting. You might want to try the Five Whys approach as well: https://en.wikipedia.org/wiki/Five_whys https://en.wikipedia.org/wiki/Five_whys