That page also suggests you read the dconf man page which might give you some more pointers.
My suggestion, since you would also need to have the user log in again anyway, would be to try the virtual terminal approach I mentioned earlier and see if that works. I am under the impression that the desktop gui may be interfering with dconf (and vice versa) since you are modifying global parameters while logged into the gui. If you don’t already know, the virtual terminal is accessible using ‘ctrl-alt-F3’ (or any F key F3 thru F6)