I modelled the twin tails as a normal mesh object, then parented it to two chains of bones with automatic weights. I then attached those bones to two thin strips of invisible mesh that have a cloth modifier. This was done by parenting several empties to vertices along the middle of the strips, then adding IK constraints to the bones to point to those empties (so the bones move like the cloth strips and so the hair will have the same kind of cloth motion)
Sorry its quite hard to describe without pictures, but its a useful technique for making meshes behave like cloths.
aha thx, but tbh I learnt the idea of attaching mesh to bones to empties to cloth from a hair rigging tutorial I think it's used by quite a few blender artists. It's pretty versatile in that it can be used to make any complex mesh behave like cloth - I also used it for Miku's skirt by attaching 8 bone changes around it, since the folds wouldn't hold with just a normal cloth modifier.