Are you referring to making your own body?
It has been along time, but I used to do a little bit of taxidermy on my ducks. Seems like we used excesleir (sp). It was like a straw packing that you could shape quite well and bind with twine.
Of course I don't have a single one of those mounts anymore, so that tells you how well of a job I did, and how well they held up.