After shading in the tonal values she moved onto using a Kuretake pen, (Kuretake is a Japanese brand known for their hugely diverse range of creative pens and markers). Her pen helps her with a Japanese ‘Sumi’ style to get to the essence of the subject.

To get more shading, damp kitchen roll was used with Indian ink which was then transferred to a brush for details, but she reminded us not to use too much liquid on the pastel paper.

Eco Line pens, which are water soluble, were used for the mid-grey tones, using loose marks. After the monotones you can add some red brown pen accents here and there . 
A good warming up exercise in this style is to do a quick continuous line drawing of the head in pen , holding the pen on the end. This will produce a free, expressive drawing. 

(Thanks to Penny Lamb for providing these notes).