I hadn't heard of it before, but I found the wiki on vernix caseosa to be quite interesting.
Admittedly wiki is a non-safe reference, but I'm not durious enough to dig around for medical refs.
Anyway, assuming no one is maliciously mucking it up or accidentally messing it up, I don't think it would really form the basis of a rejuv formula. For one thing, it isn't generally a liquid: "In Latin vernix means varnish and caseosa means cheesy."
I heard an interview on NPR today with a fellow from a company developing a liquid oxy-carrier. He claimed it carried 4 times the oxygen of a blood cell in one/thousandth the space. Uses being investigated include intravenous into the brain in cases of blood-flow interuption to to injury, and combating bends (I think the method he discussed involved use of a hyperbaric chamber as opposed to pressurized one - the rationale being this method would only be used if insuffiecient pressure chamber space were available during a deep-sea accident retrieval). He seemed very proud of a 90% survival rate using this method on animal tests. I wouldn't be so sanguine about a 10% fatality rate, but I digress...
My point is that this stuff seems a very viable start to a rejuv system, since he also claimed, as a side benefit, that the extra oxygen would help reduce wrinkles.
I know it's a quibble; what you call the stuff isn't really important compared to the story effects, but I thought I'd mention it.