Dry shampoo is great to use on the day you do not wash your hair, it's more just a way to help absorb some of the oil. It's absolutely not a replacement for washing your hair but helps on the days you do not decide to wash your hair.
I've never understood the dry shampoo concept, I thought shampoo was for washing your hair and being rinsed out. I think the dry shampoo is just to make it smell SO FRESH AND SO CLEAN,CLEAN. Outkast Reference.