Just to add to what Kenji said:
It's a good idea to catch those BD from butterfly, after the opponent eats this occasionally though, they're going to look for another way out of the butterfly mid-screen, or just guard. So once you catch them mid-screen once with HS fuujin, then it's time to think about some other options too, depending on the character you're facing. More than likely if it's a DP character they will DP the butterfly the next time.
Also a lot of this is also how your opponent plays too. You just kinda have to feel for it.