Here are some tips on that move, which I recently learned... well it took a darn long time. I am assuming you are right-handed.
Right hand over top of the deck with 3 fingers at the upper right corner. All except pinky, thumb at bottom short side.
Left hand under the deck, index + long finger on the bottom and thumb close to center on top of the deck near the bottom short side.
Go first a little to left and bend the card inwards and then keep the same pressure when circulating around the hand. Thumb on the left finger and the right hand are working opposite ways when the fan takes place.
Now go practice.. :blush:
I am so sorry... I misunderstood... I thought you were having problem with the fan splitting while fanning a pressure.