Mad Charcoal
How to Draw a Moody Landscape Work from black and white image on ipad. Use charcoal powder and piece of paper to block out shapes. Get values and proportions right. Work first with large shapes. Use compressed charcoal, a sandpaper tool, slap the powder you make with these onto the drawing and rub to get intense, much darker values. (We work from light to dark)
More links
Free-form abstract charcoal drawing https://www.reddit.com/r/CharcoalDrawing/comments/1bguori/free_form_abstract_charcoal_drawing/