Photoshop :: Refine Mask Feature - Hair Masking

Still getting mixed results using "Refine Mask" feature. I have seen the tutorials on this -Russel B, and Juleane Kost. Sometimes the results are outstanding, other times I have to resort to contrast masking, etc. I currently have a series of portraits shot against blue (basically a blue screen). Some of the subjects have good hair contrast (very dark brown or grey). There are many parameters to set in the refine mask dialog. I need a clean, sharp silo of hair edges.

I have tried many combinations, and typically use "smart radius". But I am particularly disappointed with the results of one subject who has grey hair -good contrast against the blue. They mask tool keeps including too much of the BG blue. I have also tried decontaminating colors, but prefer to do that later with a layer set to "color". Some of the tutorials sneer at the use of Contrast Masks (which I typically get good results from). But the the Refine Mask options often produce flawed results -which is surprising with these blue screen portraits.