Follow Serenity Falls tutorial, except clone a custom hair not base game hair. [After the linking stage] To get the hair to show up in game, the property sets must correspond to the correct groups in your mesh.
I need more eyes in MSWN's sclera so I decided to take it upon myself to do it! I only have Jessi's eyes in my to-do folder as of yet but i'll probably do more as it is pretty easy to do.