The sexual act of having your face coated in your lover's feces whether it be solid feces or not, thus producing several different terms:
spray painting (direct from the ass, liquid), roller painting (rolling a solid terd with the hand on your lover's face), stick painting (use of a solid terd like a pencil to make artistic designs on your lover's face).
I'm going to this big facepainting party later, wanna come?
I facepainted my girl last night and she licked her face clean.
I don't like sex, I just like face-painting.
My kid said he wanted a face-painting so I did it; does that make me a bad father?