You can follow the suggestion on that link. Once you list multiple layout in xorg.conf, you can either use the XFCE panel plugin (keyboard layout switcher) or you can define a key in xorg.conf to switch it. I prefer the latter method, here's the relevant part of my xorg.conf (I use Alt+Shift to change language):
Option "XkbLayout" "us,tr"
Option "XKbOptions" "grp:alt_shift_toggle"