A finished beer will have, at most, roughly a million cells per milliliter. So if it was stored cold there could be as many as ~350 million cells in a 12 fl oz bottle. More than likely, it's actually less than 100 million. So the key is to start with a very small volume of wort and step up several times. I like to start with 50 mL of wort, then 250 mL, then 1 L, give or take. At that point you should have roughly 50-100 billion cells and you can treat it like a pack or vial.