I need After Effects tutorial help!
 

This is for people who have basic knowledge of After Effects. I am a newbie and tried searching the manual for hours but still cant figure it out...

On the second part of the tutorial "Second Composition: Wind," I cannot figure out how he creates that white cloudy-looking, object. Can someone please help a newbie out step-by-step. Thanks!

http://www.creativecow.net/articles/eriksson_emanuel/sand/index.html

It's a mask that's slightly feathered. You can get masks to curve by clicking and holding down while you're creating a new point.