As far as I know, there is no easy way to do this if you can’t get can’t get good contrast. I did take you image and converted it to CYMK just to make a mask, and I did have a little more luck using the Magenta channel. You might want to try that (Make a copy, not the original) and them copy it back into the RGB version to use as a mask. I did not have enough time to really do a lot.
Personally, if I can help it, I just get rid of the soft whispy hairs and only use the main hair. I know sometimes it’s not possible. I just clone out the pain in the butt stuff.