I snip the head off a stalk with sisscors, leaving a bit of stalk behind.(i tried scapels and dykes, sisscors are definately the most effective)
I find a chunk of rubble. I set the chunk I snipped off on the new rock, and toss a rubber band around it. In about 3 days, its grown well onto the rock and its a sellable frag. Then I snip the rubber band and pull it out.
In a week or so, that stalk you left on the rock will re-grow a new head that you can snip again.
Done. Its the most simple to propagte of all the sofies. However, I use basically the same method for all different types of sofies. If the soft coral is thriving in the enviroment, you can just cut off a chunk from basically any coral in any part and it will regrow a new animal from that chunk. The trick is just in knowing which parts to cut to enable it to easily attach to something again.