ACK! Well, if you add Bacardi....
I've never heard of this method. One method that absolutely works is cutting propogation.
Here's how you do it:
Collect a small container (like a specimen container), super glue, clean scissors, and some paper towel, and 4 small plugs, pieces of rock, or large shells.
Remove the mushroom rock from the water, and cut the mushrooms head off that you want to propogate, cutting as close to the bottom of the stalk that you can. Put the cut off head in the container you have ready filled with tank water.
Put the rock back in the tank

Remove the head, and pat it gently with paper towel. It will be SLICK and SLIPPERY as it releases mucus. Cut it across the middle (like a pizza) into 4 pieces. Put a good amount of glue on the plug, shell or whatever you're attaching the cuttings to, and gently press one mushroom cutting onto it. Hold it for about 30 seconds. If you have glue that works underwater, do it in the container, if not, its okay. Repeat for the other 3 cuttings.
Place them back in the tank. In about 2 weeks, the mushroom that was decapitated will grow a new head, and your new cuttings should show signs of regrowth. In about 2 months, you'll have 5 mushrooms.