Years ago, before the meters and other devices were available, these practices were common. You were not a 'real' electrician if you did not test this way. I was taught the 'thumb - forefinger' method when I started. Meters are now not only available, but not too costly - especially when it is your life we are discussing. With the advent of the volt tic, the non contact devices, and the handheld thermometer, I do not see the need to use one's hand anymore.
Pierre
