This is a critical point. The hardest time I have with guys is showing them how much pressure to use. First I show them how much you can flex the calipers and impact the reading, then I give them a standard to measure so that they know what the correct amount of pressure is. Its a total feel thing at the individual level, and it is important.
Then of course you have the jackwagon machinists who will push hard or barely touch a part to pass in-process inspection. Those are the ones you know are dishonest in many things, not just their work.