First off, you'll want to install nifscripts plugin for blender. There are plenty of tutorials out there. Google it. When you ooen your skyrim save in game, open the console and type: savepcface [name] the you can import it into creation kit. Follow this tutorial to do so.
When youve done this, select your actor in the creation kit and press ctrl + f4 Your facegendata Will be exported to your skyrim meshes.bsa in actors/character/facegen/facegeom/[modname] (im not 100% sure if this is the right folder. I cant check because i am responding from my phone.) Now import the nif file into nifskope and follow the steps shown in this tutorial. https://youtu.be/N-FfbwF08Iw hope you succeed! Ive been pulling my hair out on this as well.