Painting the black leather trenchcoat on the subject is a trial and error process.
Initially I started out with a Prussian Blue + Burnt Sienna base. However this was too blue for my likely and a thin coat of Burnt Umber was painted over. The highlights on the trenchcoat was picked out by light drybushing with a mixture of Yellow Orche & Burnt Umber. (Buff works as well). This helped me to visualise the fall of light and identify the subsequent areas I want to empahsise. Matt Black was painted into the shadow areas to give it depth.
Given the limited range of colours to work with, the weathering effects of trenchcoat gave it an addition dimension to an otherwise rather monotone area. It also allowed additional colours to be introduced. (Burnt Sienna, Yellow Orche, Fawn etc...)
Drawing on references, emphasis was given to the edges, joints and contact areas of the trenchcoat. Scratches were also introduced for a worn look.