Ok, well where to start.
Mushrooms - Depending on how many mushrooms you want you can chop them up into almost any size pieces you want and they will eventually grow back, but you may have some more mortality. The best way that I have found is to cut the cap of the mushroom off of the rock with the mouth still attached and perhaps cut that in half if you choose. Then put a cup or small container of rubble in a low flow area and put the pieces in. In a couple weeks they will be healthy new mushrooms.
Xenia - Before you start go to Wal-Mart and buy a square yard of bridal veil and a bag of rubber bands for about 3$. Snip off a stalk or a branch of a stalk of the xenia. Put the stalk on a small piece of rubble, loosely put the bridal veil over it, and rubber band the veil to the rock. As long as the veil isnt pressing onto the tissue the frag should be nice and healthy in about a week or so and you can blow a little water on the polyps (which will be outside of the veil) to make them retract and slowly wiggle the veil off the polyps.
Kenya Tree - Snip off a small branch of the kenya tree, and either put a toothpic through the base of the stalk or thread a needle with some fishing line and thread that through the stalk. Then either tie the thread to the frag plug/rubble, or glue the toothpick down with a touch of super glue. The frag shoudl attach in about 2 weeks, and once it does you can remove whatever is securing it to the rock/plug.
Finger Leather - Same thing as kenya tree.
Button Polyps - Using a small hobby knife with changeable blades, first use a sharp blade and cut the tissue around the bottom of the polyps in the area you want to frag off. Then use a dull rounded blade to gently wiggle between the mat of polyps and the rock. The mat should come up once you get the hang of it and can then be attached to rubble/frag plug with a small dab of super glue, or if left on a piece of rubble or plug the matt will attach in a little bit.
There are many other ways of doing these, these are just the ones that I have had expierence with and have worked for me.