Rose, I think your drawing is very well rendered. You can go deeper in tone still to reach the tonal values that the lesson shows.
Hatching is a classic technique for shading and I find to do so seamlessly you need to cover the entire drawing surface with pencil strokes and deepen the shading in areas of darker tone. That way you avoid the 'bearded' look that I think you're talking about.
In a drawing, especially a portrait, the only part of the white paper that should show through is the catchlight in the eye and any highlight on a tooth if it shows. All skin tones should have an initial layer of graphite applied. It may look odd at first, but remember that if you do not have a background drawn it will seem darker in comparison to the whiteness of the paper. A background will really reduce the tones of your drawing.
As for hatching stroke length, there is no hard and fast rule. Do what is comfortable to you and what suits the image that you are drawing. To fill large spaces, the length of your line will be longer and shorter in smaller, tighter areas.
Remember that hatching is just one form of shading, try out others and see which suits you best. Try some of Brenda's lessons using other forms of shading and blending and see how they turn out.
I, too, rarely use just hatching to complete a drawing. For true realism, I use circulism mostly, which involves no blending and no erasing. Its slow but effective in achieving skin texture.
Pencil pressure and the number of layers used achieve the tone that you need.
I hope that helps a bit.