This patch add Xfce specific FAQ in order to help users. It was an open task in the latest status report.
In "Resources" section I didn't mention Porter's handbook (section regarding Xfce is outdated), but an update is planned for the next stable release (4.12), after switch to USES= xfce, a draft can be found at D677 (I'm waiting update of multimedia/gstreamer1).
In x11-wm/xfce4 meta port, gdm will be replaced by x11/slim soon.
It's result of GNOME3 import, gdm requires x11/gnome-shell, and especially KMS drivers (PR195325).
SLiM works out of box, Xdm needs patch (explained in question #2). I'm also working on LightDM but I've encountered problem with authentication and I prefer to focus on sysutils/xfce4-power-manager update (with support of brightness through acpi_video).
Question #3 explained how to configure Xfce for our favorite locales.
Question #5 explained howto launch xfdashboard (imported recently).
Question #7 is necessary for new feature, zooming in x11-wm/xfce4-wm (4.11.x and higher)
Question #8 fixes PR 165685.
Question #9 will replace patch in x11-wm/xfce4-wm (PR 194135) and in upstream repository there're fixes for Qt and GTK3 applications.