No, I've never written a tutorial about this. What you would have found was my specific advice to somebody else that applied to their specific photo. Which is why it hasn't quite worked for you here.
As it happens, I think yours is an easier fix. Just sample some good hair colour, and add a Solid Color layer of that colour, set to "Color" blend mode. Then mask it on slowly and patiently with a 5% brush, until the hair blends nicely.