My husband and I are fostering a dog. We received her the day she was taken from her current situation. She had spent her short life in a yard full of dogs. She was treated with renovation by the rescue group, the day we picked her up. We bathed her with dawn and followed the instructions, 3 times. We have not seen one flea but have flea dirt whereever she lays. Are we missing something? Could she have been so coated with fleas before that there is a build up of the dirt coming off her?