It is related a lot to the quality of the deck. Fanning powder helps. If it's bad enough you should simply get a new deck, break it in, and keep practicing.
You should also apply a small amount of pressure when spreading the deck.
Porper clips also increase the deck's lifespan.
And how's the shape of your fan?
Also, the pressure fan generally gives you a much more even fan. However it is often reguarded by some as the hardest fan and even flourish in the world and by other as "Eezy peezy".