When having more than one Gentoo installation at the same location, you should seriously consider sharing the Portage tree to avoid a lot of unnecessary downloads. This can be done by having the tree on only one machine and share it with NFS, the Network File System.

Server (Gentoo Linux)
First, we're going to configure the server, having the Portage tree installed in /usr/portage. I suggest following the first half of my previous article on setting up a NFS connection between Gentoo and FreeBSD.

According to one bug wrangler on Gentoo Bugzilla, you're a stupid person if you don't read the messages spitted out by ebuilds and run into failures because of that. Of course, no sane person watches the complete compilations of application on the lookout for warnings or other informative messages. But it would be nice if you get a nice summary of all messages in your mailbox after an emerge command.