Xenias

Most of the time, a portion can be gently removed from where it's growing and moved to a new spot. Wedding veil, a toothpick, or a rubber band (gentle! too tight and it will cut right through) can be used to keep it in place for a day or so until it sticks down.

Believe me, if your xenia grows like mine, then you don't want to spread it around your tank as it will be worse than an aptaisia infestation.
I keep mine on a high point with nothing in reach for it to spread to.
In my prop tank I put small pieces of rubble up against the base of the xenia stalk, and let it grow onto the rubble. Then, a simple cut with a razor blade and you have a new already mounted xenia frag.

I used the same method as rayjay. If happy, xenia is indeed a weed. I had so much that I was pulling out chunks weekly, and even gave up and put it in the FO, hoping the trigger or burr fish would snack on it. No such luck. Even under the lower light (VHO vrs MH), it spread and grew and thrived.

VHO vs MH, that MH will give you a headache from the Xenia growth.

What type of Xenia do you have? Some will grow faster than others, what I have noticed. I accidentally cut some of the heads off my xenia, the pieces attached else where in a few hours.

i think they are very hardy and fast reproducing filter feeding animals. try cutting with sharp knife or scissor. maybe cut as a stalk or a few branches at a time near the base. have some small pieces of rock handy. paper towel dry the rock where you want the coral to go. cut coral and place it in a dish. add superglue, plain old superglue gel in the amount of the letter O on your keypad, to dried area of rock. take cut coral and attach base of coral to rock. contact with superglue for a few seconds. then put the propagated piece back into aquarium in a slower flow area. the actual glue process is done out of the water, it's okay for the coral to be outside for a bit. in a few days the propagated piece should open up and wave like new.

I just put rubble next to a stalk and 1 month or so later remove it and it has a whole new stalk on it, then i trade for other corals.