Use an Eye Pencil!
Once the shaping process is complete it is time to fill in the thin spots with an eyebrow pencil. The key here is to get a shade that absolutely matches the color of your eyebrow hair. It will be very easy to tell if an alternate color has been used. If you are unsure of what the exact shade is that you need, consider purchasing a few. Do your best to match the shade and use the other shads as eyeliner.
You will want to go around the edges of the brows to complete the shaping process. Make sure that the lines are straight and that it looks even on both sides. Once both brows are evenly outlined and shaped, begin filling them in. It is best to go with the pattern of the hair so that there are no spots left untouched. Going against the growth pattern is likely to leave uneven overage and skin colored spots to be visible. Just to ensure that the filling in is absolutely complete, use an eye shadow brush to softly brush through the eyebrows. This helps to blend the pencil tracks together and make it look seamless between the follicles and skin.