|Sketch with DOT-PATTERN added|
Today you can still buy sheets of tone, DELETER for one still makes it. You can find DELETER products here in the US at comictones.com -- its very popular among Manga artists so they stock it.
You can also add DOT PATTERNS via PHOTOSHOP which is my method of choice. Simply create a halftone pattern by going to FILTER>HALFTONE PATTERN and play with different colors to try different halftone pattern.
ADD A NEW LAYER over your illustration and drop the DOTS on top of it. Change the layer opacity to MULTIPLY and erase the DOTS on the left side of the illo to make it emphasize the form of the figure.