The only real advice I have about fanning is that the cards can't be worn/dirty. Even if they don't look dirty, if they've started clumping even a tiny little bit, that's going to be magnified when you try to fan them. Also, while your grip hand should be applying a good amount of force to serve as a pivot in the lower corner of the deck, the fingertip used to actually fan the card should be very lightly touching, no serious pressure from the finger making the cards fan. It's a muscle memory thing to slowly lift the finger while still pushing the fan around, but to get a pretty fan, it helps to "slope" the path of that finger upwards as you go around. Beveling the deck in the direction you want to go should help as well.