Kindle necromancy is commonly called "debricking". There is a sticky thread, with recent K3 discussions. Currently, using the serial port is the only sure way, but we may get a USB-only debricking method working for the K3 if this discussion turns into new code.
EDIT: You can now debrick a K3 with only USB! See my post below.
For the serial port method, check out
seaniko7's youtube video linked in the "simple debricking" sticky in the dev corner forum (where most of the technical assistance gets done).