I currently go to about:profiles and click "open this profile in a new window", but this is very klutzy compared to Chrome's profile switcher next to the URL bar.
Of course you can also create launchers/shortcuts for Firefox with "firefox -P profilename" but again that's work you have to do on each machine you use.
A classic solution is just one shortcut of `firefox -no-remote -ProfileManager` which semi-replicates one of the old Netscape-feeling behaviors in that such a shortcut will always create a new instance of Firefox and first launch the select profile window.
Of course you can also create launchers/shortcuts for Firefox with "firefox -P profilename" but again that's work you have to do on each machine you use.