If you dyed your hair, what colour is it? When using dry shampoos I've found that it leaves ugly white flakes that look like dandruff IF the hair is brown or black. They're pretty hard to get out. So, if you have to wash your hair again afterwards, it's pretty useless.
I always try to let the oil build up for a few day when I know I won't meet anyone.
Just a few months ago I started having the same problem as you. I'm slowly working my way back up. For two days they are nearly alright, now.