I use a disappearing quilters pen for my faces, when I'm embroidering or painting them.
Simply sketch out your face design out with a disappearing quilters pen then if you make a mistake you can always re-draw :) Either using your pattern as a guide - see tutorial included in your pattern - or why not try a new face from your imagination!
I use this pen and have never had a problem with the ink - Dritz Marking Pen Disappearing Ink Pink Product Detail :) There are so many on the market so please don't think I ONLY recommend this one :) I don't! I say .. try 'em all till ya find the one you love :)
Plus these pens works on wool felt too!!!! (ok, this was photoshoped on, as I couldn't get the pink to show up in my photos hehehehe)
REMEMBER: Always use pre-washed fabric and do a test first with your pen on some scrap fabric as sometimes depending on your Pen and Fabric Choice the ink can 're appear!' or doesn't disappear at all!!! ....... And that's no fun :(