I've got always at least three different Google accounts logged in: personal one (GMail + G+ + Google Docs), professional one (Google Apps for Domain / Business : GMail + Google Docs) and a "fake identity one" (GMail + G+).

The way I do it very simple: separate user accounts on Linux. That way you're sure there's no way they're going to interfere with each other. Of course it helps to be using an OS on which it's trivial to have multiple indepedent graphical sessions and which allow (if you grant that privilege) another local user to display it's app on your graphical session.

The "temp" / fake identity account is actually running inside a VM (KVM) because I use to surf on untrusted sites and is really a "throwaway" account / VM.

That kind of blog entry is kiddie stuff compared to what's easily doable under Linux.