Hi

Great question. I can only talk from experience. My wife has thick dark, dirty blonde long hair to her bra strap.

She has embraced my kink and seen the benefit for the last 18 months now. She claims that the best way to get the full benefit is onto hair thats turned and in need of washing. I deposit at the root and she combs it from root to tip.

She then leaves it for 20-30 mins before blow drying her hair. She then washes it later that day or early morning.

Just my view from experience.