Animate a liquid

I did this a couple of years ago, so forgive me if I don't remember 100%. I remember having trouble with transparencies and how it rendered in Ch, so my character only seems transparent but is really opaque - the program has gone through quite a few changes since then, so you might have an easier time with the transparencies.
I drew the shape of the bottle in illustrator and then drew the liquid shape above it, faking a top surface with a couple of gradients. I made sure that the liquid shape was wider than the bottle. In Ch I added the dangle handles in the parts that went out of the shape, as well as one in the middle, and fixed the bottom (I added another shape that continued the liquid but doesn't move.) I then clipped the liquid movement shape to the bottle shape and added it's own physics behavior, playing around with the squashiness, stiffness, etc., until I got a movement I was happy with. It's triggered by face movement, like hair dangles.