He feels Watson's moan as much as he hears it and repays the favor, moaning around Watson's cock as he moves his hand to draw him in deep. Holmes would be reluctant to admit it, but his inventiveness is wearing thin; his mind is diverting more attention to the mouth on his own cock, and it's rather unwilling to change that.

He begins moving his mouth on Watson in earnest, finding a steady rhythm that's certainly not intended to be very teasing. He does, at least, cup Watson's bollocks, teasing them with his fingers because he isn't about to give up this inventiveness game so easily.