Hi ,
Perhaps helps you if you make a print of your photo but about 20-25 % brighter than original, in Paint Shop Pro (or equivalent). Less contrast and using the "Colorisation" function (I took Hue=25 and Saturation=107). Now you get a "milky" or foggy picture and having "room or space" to go darker (glazes) or brighter with opaque flesh tints.
I also think that is difficult to change the forms after the first glazes.. Hope you're not angry 'cause manipulating...

You can even see the reflected light on the shadow side. If you get problems to alter your photo send me and I send back per mail.
Cheers.
PS. Michael Georges works with underpainting, too. Verdaccio.