For the cleanest prints, an etching press works best. You put a spray nozzle on bottle of rubbing alcohol, spritz the paper evenly with 6 to 8 sprays. Wait till all the shiny puddles soak in fully, then put the paper on top of the image, and run it through the press. The bold Sharpie colors transfer really well.
Without a press, tape the printing paper to one edge of the Plexiglass. Put the plate and paper flat on a table and mist the plastic side with the alcohol. Turn the paper over onto the plate along the taped hinge and press firmly on the back to transfer the image. This will give it a slightly fuzzy print, but the transfer is pretty easy. The tape helps pull a neat print and minimizes "shimmy" or jitter while printing.
The nice thing about Plexiglas is that one can trace. We have done animals from magazines, combined animals to make new creatures, traced self-portraits and used color expressively, but the most fun we have had was with our squish face prints.
Have one student hold the plastic tightly against their face, twisting or pushing the plastic may give an extra stretch to the image. Their partner traces their features with Sharpie, and we use the press to print. Plates are easily cleaned with the same rubbing alcohol and a tissue or rag. (Room should have good airflow for this exploration.)
Here are some other images we have created with this same media technique.