Mythcons (11/28/2019)
I don't know if these have been covered:
1) You can achieve most head proportions, without using a tool like Zbrush or Blender, by pushing/pulling various attributes (mouth, nose, face shape) and repeatedly 'baking' the morphs. This resets the morph sliders at 0, allowing you to continue. Rince and repeat.
2) If your reference photo has an expression, try to replicate the basics of that expression and then re-project the photo using the Headshot Photo Matching tool.
3) If your photo projection is partially successful (e.g. half the projection is clean, half has shadow / distortions), export the projection to an image editor like Photoshop. Copy half the image, flip it horizontally. Now you have a better base to work with. Asymmetrical details can be added in selectively.
Very helpful. Here is a tutorial by Mike Sherwood explaining the techniques you mention, among others.
Your item # 2 was especially of interest to me, because I have been trying the obvious method of correcting a smile in my image editor with a warp tool.