Brush the entire mold with the dental foil separator. Let it dry. This will keep the acrylic from sticking to the mold. Sculpt the fangs you want on the plaster mold. They don't have to be perfect, as you will be filing the finished product down to perfection. But the closest you can get to the fang you want the less work you'll be doing on them after they're cast. Just take a small piece of Klean Klay, roll it into an oblong and press over the tooth. Make sure you cover the back of the tooth as well. After all, these will be caps. Not too thick in the back and just enough in the front of the tooth to give it shape. If you make the fangs too bulky they'll be uncomfortable to wear.
