The dry shampoo's first obvious use is to "wash your hair. Some of us can not wash their hair everyday: it would lead to an ultra-sensitivity of the scalpe. Therefore, every other day instead of washing your hair under the shower, you would spray some dry shampoo at the roots of your hair in particular. It is where the grease and oily deposit is created.
The main issue woman dread is the whiteness of the powder. At the start, dry shampoo is simply baby powder. I personally know many women who are scared of this product because of this aspect. However, the solution is just very simple: brushing it away.
First, you will apply the dry shampoo and let it set for a few minutes while brushing your hair. For more volume, do tilt it upside down if you are aiming at getting a tad more volume. What will "wash" your hair will get onto your scalpe and the excess powder will fall of. Don't over brush you hair though and try not to put your hands through it too much during the day (it would make them greasy).
As the application of dry shampoo willget rid of any oily excess through your hair, they will seem much looser and gain volume, the way your hair tends to get just after you shower when it is just dried up.
Therefore, I would highly recommend to have a small bottle of dry shampoo in your bag at work. If you need to look good, have an after-work drink. Just go to the bathroom, bend your head, spray some at the roots, shake it and brush it out. You are fabulous again and ready to go.