The ponytail is done by the same process of using a thicker wire (18g) wrapped round twice with 20g wire for the clay to 'key' to and to provide extra strength.
It will hold its form but is still flexible enough for you to be able to alter the shape (st1.19).
The shape and length of the ponytail wire was a bit of guess work as I've been working from only one perspective and was done really just by holding the wire against the sculpt and altering until I was happy. (see st.1.20).