Hair meshes in DAZ Studio often lack bones that allow them to be posed, and even if hair bones exist they can only be posed in very limited ways. To remedy this I have spent some days implementing a tool for automatically adding hair bones that can be used to pose the hair mesh.
Select the hair mesh and press the Add Hair Rig button at the bottom of the Hair section. New hair bones are created for the parent armature, and vertex weights are assigned to the hair vertices. For details see the Add Hair Rig page in the new documentation