Eric Schlaepfer showed Hackaday Remoticon techniques for reverse engineering 2-layer PCBs:

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so i made a thing. a very big PCB with 4304 components. A 6502 microprocessor. https://t.co/x78OwmwyHW pic.twitter.com/KWztWA3E9f

— Tube Time (@TubeTimeUS) May 16, 2016