Rob has a good video on fragging... not sure if that transfered over to this website though...
But fragging Xenia is pretty easy.... you can either pull the xenia off the rock, or cut it with a knife/scissors at the bottom of the stalk and then take the piece and rubberband it to some rock- don't rubberband it too tight or it will come off, just enough for it to stay- and then it will be attached within a few days- week.
Because Xenia grows in the direction of the flow, some people will just put a rock next to it and it will spread onto the rock.
Some people also
frag using wedding vail and wrap the coral to the rock with the vail.
You can also use a toothpick which prolly works better than the rubberband by itself. Put the toothpick through the stalk and then rubberband from the tips of the toothpick under the rock....
Maybe that helps?