This drawing of the Buddha is just a quick study to help me consider the value relationships with a larger oil painting in mind. So far I have just used pencil grades HB and 3B as well as an eraser. The eraser is used as a drawing tool to cut into the graphite and draw a line. After the last stage where I established the large shadow shapes I blend all over with a tissue then mark out the lit planes using the eraser. The final stage strengthens the darks and the edges finishing with the darkest and lightest accents.