List of what I used for that bio:
15lbs of Klean Klay.
Smooth-on Dragonskin silicone.
Plaster of paris & cheesecloth.
For actually casting it, Smooth-on smooth cast 320 resin.
It really is that simple, everything is listed if you read the thread.
The oomoo silicones will work fine, but have a tendency to tear rather easily. I have a bio mold that I made with some left over oomoo 25, and I've had to repair it about 3 times already. I wouldn't recommend the dragonskin silicone unless the bio has a LOT of undercuts and the mold will take some serious abuse just trying to get the bio out. The celtic bio is a good example of something where dragonskin is ideal. Otherwise, the mold max silicone will do just fine. Also, dragonskin has a bad reaction to chavant clay, as does rebound 25. I've heard the mold max is better, but it's worth taking into account when choosing your clay.