We have been using gpupdate /force on the clients.  What if you have hundreds of clients?  The book describes this in chapter 5, but is using a powershell commandlet  CMDLET.   This article describes how to do this via the management GUI.  Step one involves the firewall settings, step 2 is the update.  There are two articles.  Compare them to see any differences.  If your firewalls are off on your clients you wouldn't have to worry about it, but it is cool you can manage firewall settings with GPO's too.

https://msptechs.com/how-to-update-group-policy-remotely-on-windows-server-2016/

https://www.petri.com/force-remote-group-policy-update-gpmc