First of all, just to make it clear, American Crew Boost Powder is definitely not the product to be used alone (I use it together with 'american crew fiber').
At a first glance, I was really sceptical ('powder for hairstyling, what?'), however, I was more than surprised by results.
American Crew Boost Powder just lifts my hair up instantaneously (and my hair tends to just lay 'flat dead' on my head), adds reasonable amount of volume. This volume even helps to decrease the visibility of my recently-appeared-and-growing bald spots.
Contrary to instructions, I use it on towel-dry hair. Sprinkle some powder (really small amounts) on my fingers and try to spread it evenly on the head. Make sure it reaches the roots!
All in all, it's my hair product of the year.