I'm pretty slack about using a gauge to check tyres, but do rely on the claim that underinflated tyres run hotter because of the increased sidewall flexing.
Every stop I walk around and lay my hand on each tyre and compare temperatures - taking into account which tyres the sun is shining on of course.
Gauge accuracy doesn't matter as much as gauge repeatability and using the same gauge all the time. Usual tyre management uses the tyre manufacturers tables to set the initial pressure based on load and then occasionally check the tread wear to see if it is uniform across the width. Worn more in the middle - too much pressure, worn on the outside, too little.
