I suggest you get a flesh tone pencil, Though you could always try making one through yellow, orange, pink and brown, but that can be difficult. Even if you have flesh toned pencils, It can sometimes be worth having those around, as accents and blushes.
Another Suggestion
The process is a bit time consuming, but ultimately worth the effort. First observe closely the colour of your subject's skin.
For lighter colours ( blondes)I start with a very light base of light purple, then in the areas of shadow I add a touch of pale green, Blend this completely then add a light layer of peach, blend again. In the areas of shadow use terra cotta and more light green, continue blending and adding more colour. Adjust with the light purple and terra cotta for warmer tones, with greens for cooler tones. Your highlights will be light yellows and peaches your shadows need greens and blues. Don't forget that colours around your subject (found in clothing etc) will reflect onto the skin. Work slow and blend well for the best results.
For medium toned skin ( brown hair) start with purple and olive green, add peach and terra cotta, highlight with medium yellow, shadow with olive green and brown.
For dark toned skin (black hair and eyes) start with purple and olive green, add terra cotta and brown. Highlight with yellow and shadow with green and brown.
