On the installation I know that you can have the installer export out the wsp to manually install them. I want to do the PowerShell install so that it deploys this to 1 server at a time to limit the downtime. When we were on 2010 the msi installer would take roughly 5 to 7 minutes to install and deploy to 4 servers. Later the installer was changed to an exe and then the installer time lasts around 30 minutes. We've migrated to 2013 and the installer is still around the same amount of time. With being a 24/7 operation, it is tough to ask for an hour of downtime when all that you are doing is installing an update.
As I understand it on the deploy PowerShell command there is a section that allows you to deploy it at 1 WFE at a time, but I am lost on how to accomplish this.