Hi there,
i don’t know if this is of any help, but i had to do vomit once for a cartoon series. I had to do it in After FX, so i used Mr. Mercury which is a plugin used to simulate some kind of fluids. more metaball looking like. If you fiddle around with it you can get some decent result. Try playing with speed and gravity stuff and maybe use this as a mask/displace for your video.
cheers, steve.
Steve – Art Director – http://www.remedia.lu