Meter, fingers, apprentice, metal grounded box whatever is closest. If it's early AM fingers is the best for a wakeup.

Yerp. Sometimes still done today. It's not up to code as we need a neutral in the switch box.(Now) Black feed white switch loop. Neutral already existing at the light connected to another point in the same circuit (hopefully).

Edit: You can't always go off color of wires. I wire 3 and 4 way switches using white wire.(14-3 with ground) I identify with tape. Some electricians don't.