The drill I listed in Simmons thread on knuckles would work in this case too. But more then likely, your fanning issues are caused by overuse of the hands and arms in the swing and not enough rotation.

Another simple drill, and you can hit balls with this one, (pick a time on the range when there are not too many people, cause your gonna look stupid, lol) setup at address, then without turning simply lift your hands and club up over your right should keeping the left arm fairly straight (not stiff, just extended) correctly done the club will be 90 degrees to the ball target line, and parallel to the ground, now turn your body so your back is facing the target, now the club will parallel the ball target line. The only difference between this and a normal swing is doing them together. The hands, arms, club and body all work the same. Separating these actions seems to give most people a better understanding of what is going on, may help. Usually people who fan or layoff have a disconnect between body and arms, usually the hands/arms moving faster then the body can keep up, which causes the arms to cross over the chest, and the body just quits turning. Let me know if this helps.