It works out really, since Draco selfishly enjoys leaving marks wherever he can. He does hesitate at Billy's question, halting everything just for a moment as he genuinely considers the possibility of lying. But there's not much point now, is there?

"These in particular I learnt from someone I nearly considered a friend, once upon a time," he drawls quietly, and mostly un-bitterly. "I also know of several books on the subject, but I've hardly read them all."

Even as he answers Draco's pressing in both fingers quite deliberately, thrusting faintly before he's curling them within tight heat, with an almost thoughtful hum. At the moment, he's just feeling.