Although the market for hand-drawn portraits largely collapsed ... which provides just enough pen-to-paper pressure to reliably draw lines without lifting off or scratching the paper.

Once you are satisfied with the basic portrait drawing, remove the image. Trace over your pencil lines with a drawing pen or extra-fine tip marker. Once you have traced all details use an eraser ...

Try experimenting with different colours of ballpoint pen to create layers of texture. Light-coloured felt tips can easily pick up darker colours from a drawing surface. This can be avoided by ...

but because if he used only one pen the whole time, the nib would start bleeding from the constant friction. That's how much intensity creating these portraits requires. Intensity, and a lot of skill.