Don't force it. If it was meant to be, it'll fit. Don't just jam it in there. Let it ease in smoothly, naturally.
I was recently on a panel about Extreme Horror and was asked about when the violence and gore and grossness becomes gratuitous. My answer was when it doesn't evolve naturally from the story and feels forced. When the nastiness is shoehorned in just so the author could claim to have written something grosser than the next guy. I have to say, I hate that shit and I am seeing more and more of it.
Listen, if you want to write a really gross scene write a strong plot that would make that scene necessary. Write a strong character that would do the horrific acts you want to describe naturally as a direct result of the personality you imbued them with. In other words — make it make sense.
If you write a scene where a regular guy accidentally kills someone and then, for no reason, and with no prior foreshadowing, decides to mutilate and fornicate with the corpse, then cannibalize it, then continue to have sex with it as it rots, that's just not good writing. It might make for a great opportunity to write some really gross shit, but it will be at the expense of a really good story. The violence, gore, and grossness should serve the story. The story shouldn't just be some piss-poor excuse to write gross shit.
Remember porn movies in the 70s and 80s, and even into the 90s and early oughts, that used to have elaborate storylines? Full length films that were just vehicles for the hardcore sex that the viewers really bought the movie for? A woman has never acheived an orgasm until a doctor discovers that her clitoris is located at the back of her throat. Thus begins her journey to find sexual release by deepthroating one man after another. A woman is possessed by the devil and uses sex to steal souls. Women in prison who must use their bodies to seduce the guards so they can escape. And on. And on. The stories were just ridiculous and the movies were bad, but we watched them because we wanted to see the naughty bits. Well, we are beginning to see “Splatterpunk” novels that resemble these movies. Bad stories that are little more than a vehicle for the gross out. But here's the thing, it doesn't have to be that way. It is possible to write really good literature that also happens to be gross as fuck. Why make another Debbie Does Dallas when you could make Caligula?
When people call Extreme Horror or Splatterpunk “Torture Porn” they are not complimenting us. They aren't imagining Caligula. They're comparing us to 2001 Cumshots. Equating Extreme Horror with movies that are little more than scene after scene of sex without a story. And, too often, they are right.
Too many of the books I have read lately were just lists of atrocities rather than stories. Others were great stories interrupted here and there by needless and ridiculous “grossout intermissions” shoved in just to keep up with the Splatterpunk Joneses. Can we just stop that now? Can we get back to writing good stories? I mean, isn't that why you became a writer rather than a pornographer? Stop cramming in disgusting details where it does nothing to serve the story. Stop forcing it. Caress it. Massage it. Ease it in. Put it where it fits. Just let it happen.
Preach!