Best practice for upgrading BIG-IP 5250v with virtualizations

Hello we have 2 BIG IP 5250v with 2 virtualizations on every machine . Currently version 11.5.2 is installed andwe want to update to 13.0. It was already successful in our virtual Lab environment. Unfortunately, we do not find instructions, which process is the best way. First update the Big-IP and then the virtualizations or first the virtualizations and then the physical machine. Which is the best practice? Thx for your help and support.