>>307658056
Not OP, but I'd use the "point to target" edit tool in blender 2.8+, put the target somewhere in the center of the head and reverse the normals so they're all pointing outwards from the target. You can also use "spherize" to retain some of the actual geometric normals if you want. https://docs.blender.org/manual/en/2.80/modeling/meshes/editing/normals.html