Try to do other pictures. Vary the size of the grid on the picture you are copying. You should notice that close grid lines provide greater detail, but wider lines get done faster. This is the completed sketch, it has been smudged for a better shade gradient and the hair stroked on for texture. Now it will need the grid lines erased.
Gradation is obtained by decreasing the pressure on the pencil.
A softer gradation is obtained by merging.