A bit of nail polish, a container of salt water, a 9V battery, a Q-tip, and some alligator leads. That’s pretty much it. Easy, inexpensive process from Instructables user lasersage appears to give impressive results.
I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I write for MAKE, serve as Technical Editor for MAKE magazine, and develop original DIY content for Make: Projects.