If I can help, here is how the card is clipped under the fan when I do this change:
The double card is face up on the table and the fan is help only with the thumb on top, 1st and 2nd fingers on the bottom. When you steal the face card from the tabled bottom, it is very easy to drag it to the table edge, and clip it between the 4th finger below, and 3rd finger above this card, so that you can go away with the fan and the stolen card. Then you reverse it under the fan as you close it with both hands.
Hope this short description will help you.