Hey, guys!
This is my first post on this forum, and I am sure there's no duplicate of my thread. I got the way to do it, but I'm more Javascript/PHP programmer and I don't really understand AS. I have to make a picture of the bottle, duplicate of the picture on the bottom layer (which is gonna be the filling) and a MovieClip between them, which is gonna change it's height (which is gonna be the mask of the filling). The most realistic method, which I can advance is to make a sine wave effect on one of the graphics, filling or mask, and I found a lot of effects, but I don't know how to apply them on my graphics. Please help, guys!
I would make a movieclip of moving waves (the waves moving horizontally, left to right, right to left whatever!), which just loops and is deeper than your bottle.
Then set this layer to mask, and beneath it have your liquid texture.
Then I would use actionscript to make this move upwards. lee brimelow has a great preloader tutorial on his site, gotoandlearn.com
Hope this helps, its quite a vague answer but I'm not entirely sure of where you're at!