i really don't know what the problem is with your technique, it seems it would work ... but i have a suggestion or 3... try setting your material color to white sometimes this is all that's needed, make sure your ambient color is true black sometimes blue or green can appear black ... and finally the default posette head mesh will not fit most faces, the proportions are usually all wrong, to get an accurate representation you may have to morph the mesh to make features line up ... good luck

Y'all have a great day.