Google is your friend (or rather not). Have you never seen 2 girls 1 cup? I bailed as I have a weak stomach for that shit ... but it exists.
2 girls one cup, and most "Scat porn" involving professionals is done by doing an enema, nd then injecting the girls assus with a shit-like subtstance.. ice cream, nutella, brownie mix, whatever. They then immediately puke, so the puke, while gross, is stil mostly just brownie mix with some stomach acid.
Honestly think it's kind of gullible to ever assume otherwise. Is the fetish completely fake? No, but the vast majority of the gross porn you see on the internet, and likely all of the porn ivolving any remotely "pro" looking actresses is fake.
Here's the creator of 2 girls 1 cup quoted on The Smoking Gun:
http://www.thesmokinggun.com/documents/revolting/2-girls-1-cup-real-poop
There are people who actively indulge in some Coprophagia, GG Allin built a career out of it, it is not unreasonable to think that somebody can only get off with shit, I mean Coprophilia is something that exists for a reason.
Sure, but videos of random hot chicks who look like porn stars smiling while eating shit? Nah..