To recreate the look of A Scanner Darkly, you must think of lines as long, thin, irregular shapes filled with black. Using the Pencil tool, you can manually produce a calligraphic line by automatically filling in the region between two arcs.
Draw smooth decisive arcs to indicate where you imagine the points should be set. Too much wobbliness yields an uncontrolled shape with rough edges.
To edit an ugly shape, use the pen tool to delete extra points and simplify the form. It will take practice to learn how to manipulate the pencil tool accurately, but be patient and you will develop an intuitive understanding of how to manipulate the shapes quickly. Deselect after each shape by pressing Command-Shift-A (Windows: Control-Shift-A).
Check that you are on the ‘Inks’ layer and ‘ink’ the image, just like a graphic novel. Draw thin black shapes around the major forms. Also fill in the darkest regions with larger black shapes. If you need more control for areas such as the eyes or nose, you can switch to the Pen tool to draw exact curves and straight lines. This step requires the most nuance. Remember to always lock each layer when you’re finished or not working on it to avoid confusing errors later on.
Toggle the Eye icon on your Layers palette to hide the Reference layer and check your progress as you go. If you accidentally release the line before you outline the shape you’re tracing, you can draw another shape that completes the shape in the same colour. I prefer to press Command-Z (Control- Z on Windows) to undo the last action, because I find it best to make the largest possible continuous shape to increase the smoothness and overall flow of the shape.
I call my next layer ‘Shawn’. Each new subsequent layer will be placed behind the last visually or below on the layers palette. You want to always fill in behind what you’ve previously finished. Within each layer, create sub-layers categorized by features, such as eyes and mouth, to better manage all the shapes that you’re creating. I will usually break that down further into four or five shades of colour, each on its own sub-layer.