I'm a groomer and have used Dawn on very oily dogs - however it does pull the natural oils off the coat and may dry the skin which causes them to scratch. have u tried Quadruped Shampoos? I changed to this shampoo years ago and LOVE IT. I use the protein shampoo on my oily dogs and rinse
really well. Sometimes if u dont rinse really well the coat gets oily and matted.
www.quadrupedpetcare.com
good luck