Part 3: Creating the spline guides
As I said, start up your 3d program, and preferably create image planes with profile and front references. Then line them up to match each other.
OK, start tracing the profile. Start from the back of the head, and when you have gotten to the end of the chin, instead of tracing the neck, trace the jaw.
Now in the front viewport, select the jaw vertices from the spline, and move them in 3d to match the jaw in the front viewport.
Good, now trace the 3 lip lines and move them in 3d (with the help of profile reference)