'Don't know if this will be any help at all, but once when I wanted college
students to understand the concept of intaglio printing, we used Styrofoam
tray material. Line designs were impressed on the Styrofoam with pens and
pencils. Ink was applied heavily with a brayer, making sure that some got
down into the impressed lines. The surface ink was then wiped off, leaving
only the ink in the impressed lines.
When it came time to print the plate, because Styrofoam "gives" more than
hard plastic, pressure applied with a press or with a brayer on the back of
the printing paper generally yielded a high percentage of successful prints.