If memory serves me correctly. The back of your hand, talking about a Caucasian person, is in Zone VI. If you expose for Zone V or 18 % gray, your exposure will be off by one stop. Also, if you have a point and shoot digital camera, you can set the ISO to your film speed and use that as a general light meter. I had to do that today as all four of my meters, two old Pentax spot meters and two old Weston II meters, are either dead or needing calibration.
One person stopped by while I was setting up my Crown Graphic and he showed me an app on his iPhone that can give you an exposure using the iPhone's camera. Granted, I don't know how accurate that app is. I also asked him, how accurate it was and I don't think he had relied on it for his exposures.
Personally, I prefer an analog meter over a iPhone app.