One would think the wax companies would have done the research to KNOW what temps to use, how much melted wax trail to leave, etc. Why don't they include instructions with each packet of wax? I know some or all of them have info. & videos on their websites. I guess that's the place to start, plus the experience related online by those like you who have been doing it for 30+ years.
I suppose there are so many variables: ski size (bigger skis are bigger heat sinks), ambient temps, iron temp variations, what was on the skis before - or not - which wax, yada yada... that it's hard to make hard and fast rules that apply to every possible situation.
There's only so much handholding one can do.
Back in the mid 1980s a french company invented a wine label that had a built-in liquid crystal thermometer, all the bottler had to do is mark the proper, exact temperature at which the wine would most likely be best. Yeah, neither bottlers nor public took to that either.