Draco's smirking rather a lot when he works a hand under Billy's hips to get a firm and proper grasp on his cock. He'll need his wand for this, but for a moment he only squeezes tightly, feeling, and then in time with a quick stroke he whispers a new spell.

Now when he sits back, repeats a quietly familiar lubrication spell, and strokes at his own cock a bit roughly, Billy should feel it all, as if it were his own. Draco bites his own lip around a groan until the sensation passes, and his smirk returns. "This one can be quite fun."