Over-accelerators usually either flip it or wing it. I'll often work on their swivel and their face. I'll try to get some "left foot down" in the transition. Shake the sugar kind of gravity drop helps.
Basically.... face, gravity, arms from the sockets, dont run into shaft and a good swivel.
Also, many overaccelerate their irons because their swing radius never gets past the ball or under the ground ("the Run Up"). Therefore, they feel like they will clunk the ground and frantically try to do a fast flip to hit it. So like cmartin said, if they practice at all and are decent athletes, trying this could definately help.