Refine Edge is an amazing, game changing tool, by heck is not exactly intuitive. I find I am getting much better results since when it was first introduced, but the thing is, I am not entirely sure why. I have used it hundreds and hundreds of times now, and I guess all that practice has made a difference over the years.
I do know that I use a much higher initial radius setting that ever I used to, probably starting out at a full 50%. Then check Smart radius, and pull back the radius for best effect. You can't use Feather or Smooth with fine hair, but can use some Contrast. Always Check Decontaminate colors with fine hair, which automatically makes the output New layer with layer mask. This is important.
You can use tricks like copy the BG layer and increase its contrast, and use this layer to make the selection, then with the selection made, use the same selection on the good layer.
Google Martin Evening Refine edge for a good tutorial on using it with difficult backgrounds. You'll see why you need layer with layer mask.
Maybe wrong, but I think that the name of the "erase refinements tool" should be corrected, as it is used not only for the refinements made by the refine radius tool.
For me, this name has always a confusion potential for the users.