The machine starts wiring as a voice tells him "beginning male to neuter transformation. Step one: Removing secondary sex characteristics." There's something weird about thinking of his own sex characteristics as being removed.
He can feel first a pleasant massaging over his body as his hair slowly falls out. From head to toe, as something scans over him. His facial and chest hair is entirely gone, and his leg and arm hair is mostly gone if not completely gone. Only on his eyebrows, the top of his head, a bit on his underarms, and his crotch is hair unchanged. Though even the hair that remains is smoother. It feels nice, he's so smooth now, and soft. He thinks his skin might have softened too. It feels so much nicer to be hairless, like everything is a bit more sensitive.
The machine then begins to inject something into him that changes his body more. He starts feeling a strange yet alluring feeling of his bones and fat and muscles reshaping. He's afraid for a momment but it feels nice the same way stretching feels nice. His realizes that his body is becoming thinner and less muscular. He likes the thought of a slender androgynous build. And he feels a lot softer and more delicate now. It's odd to realize how diffrent he must look, he can already tell his limbs are much skinnier, and his face is much diffrent looking.
As he let's the catharsis of the transformation wash over hum he hears the voice say "beginning alteration to the genitals".