Casting A Suspended Animal Skull In Resin.

I’m trying to cast a mole, rat and chick skull in resin. Was curious if I could put 65mm, 50mm, and 40mm silicon mold in a pressure pot with the skulls incased in resin at the same time. Wasn’t sure if I should do one at a time. or if the pressure pot/resin could possibly crush the skull. I tried pouring by hand and painting the skull in resin and I still can’t stop getting a crazy amount of bubbles.