They created a prosthetic penis that he had to wear and his character’s wife (played by Sonya Walger) had to handle. It was rigged to “ejaculate” by having a prop man hiding behind a couch to pump hair conditioner through it.
They said it was pretend; simulated, so how come we can see sonya really giving him a handjob. Not pretend I see, properly pretending to make him cum, that's about it.