For the head, I would start with a ball of crumpled paper or foil wrapped around a thin stick (like a kebab skewer). The stick acts as a handle, reinforcement for the neck, and eventually the spine of the zombie chicken. Cover the ball and a neck's worth of the stick with a thin layer of clay. Sculpt the head/face and let it dry. Use a bigger stick for bigger dolls.http://wingsnthings.tripod.com/proportn.htm
is a guide to zombie chicken proportions.
For the limbs, bend a wire to pose the limb, and use the proportion guide to mark for shoulder, wrist, etc. Leave the wire quite long where it will join to the body. Sculpt the limbs, let dry.
Antique dolls usually have a cloth or leather body; do that or follow proportion guide to attach limbs to spine, trim off excess wire and skewer, then sculpt body. Do let the head and limbs dry before assembling the zombie chicken; you won't have to worry so much about damaging them.