Double the layer with the soldier's drawing. On the cloned layer we should insert a neutral color, applied with big smears. The upper layer, containing the black-white outlining and Opacity of 40% should be changed on Multiply. We may easily now add the effect of volume on the layer, containing the colored smears
and not to be afraid to lose the picture. Use a usual brush of circle shape and Flow of 50%. On this stage it's necessary to divide the shape on different surfaces. Merge down those two upper layers.