Moving Wordpress MU to a New Server

I know there are a few posts on this subject, but I am not entirely clear on the procedure of moving WPMU to a new server.

This answer is really useful...

https://premium.wpmudev.org/forums/topic/moving-wpmu-to-another-server-and-upgrade#post-79450

.... but I wonder what step 3 means exactly? Is there any documentation on how to do this?

3. change your local machines host file to direct the sites URL to the new servers ip address, so you can access the site at it's current name whilst everyone else can access the old site still.

Thanks