bone cutters (linesman pliers, or a big enough set of dykes work too) work good as long as the heads have grown a good bit of bare skeleton between the heads and the split. I have found all euphillia (branching, not wall) to be fairly easy to frag. If they have not grown out yet you should leave them for a while so the individual heads can fully develop.
(the saw stated above would be a nice idea as well, it would leave a nice flat surface to mount)