At the risk of sounding sarcastic- which is not my intent- the very best plan would be to never say words like "power" and "handspeed" near where he is training. Use terms like "loose", "don't put anything on it" and so on. Honest to God, the keys to the bus are agility and flexibilty not muscle mass and what ever else. Watch the fights and fighters; as a guy adds muscle his technique declines as he begins to punch by swinging those heavy arms. Power based on proper technique lasts, heavy arms get harder to swing etc...