This was created using Autodesk Sketchbook Pro 6
Step 1: Drawing Pockets and Zipppers
Draw the pockets and zipper using Symmetry Y and Pencil Tool with black color .
Step 2: Blocking Colors
Create a new layer and block all the colors with Paint Brush tool.
Step 3: Shading
Create a new layer Blend mode screen draw some highlights with medium red color using AirBrush.
Create another layer Blend mode multiply draw some shadows with brown color using AirBrush.
Step 4: Texturing
create a new layer add some textures with dotted texture brush.