Print with a laserjet onto overhead projector foil, spread a suitable kind of wood glue, dry, peel and apply to own finger tip. It is actually very straight forward.

From the NewScientist article Laforet linked above:

> fake fingerprints can be created by imprinting copies in rubbery gels or silicone plastic, says Marcela Espinoza of the Institute of Police Science in Lausanne, Switzerland.

Replace silicone with some other flesh-like material that's conductive.

Ok but isn't that significantly more trouble than seeing or guessing a username?

Does this take just a "wee bit of motivation"?

This video[1] is German, however as far as I can tell everything you need to get from an image to a fake print is easily available. The relevant part starts at 65 seconds. Only a few minutes to get a working fake. It is basically the process described by petschge.

[1] https://youtu.be/OPtzRQNHzl0?t=65