Been forever since I been on this site and in that time I started working at Smooth-On (it's great to have an interview with a company that has Zombies staring over the tables)
anyway, we just made a good fun video that highlights some of our products in making a zombie appliance...
http://www.youtube.com/watch?v=WxMYdVnft7c

the 'blurb'
Smooth-On's Dragon Skin® FX-Pro and Slacker® silicone modifier can be used to create silicone gel filled appliances which move and flex with an actor's every expression. In this video, Dragon Skin® FX-Pro is combined with Slacker® and cast into a Shell Shock® resin mold to create a silicone zombie facial prosthetic makeup appliance. The appliance is then adhered using Skin Tite® silicone bio-adhesive to create a realistic skin effect.

enjoy!

Rick