Captain Rex: using fineline pens with a white acrylic pen over the top.
Star Destroyer: Fineline pens using geometric shapes and line density for shading
R2-D2: using pointillism to create shading
C3PO: using cross hatching for shading
Vader’s Helmet: using scribbles and random lines for shading
Kylo Ren: Using hatching for shading and white acrylic pen for detailing (particularly on the hood)