How good are you at quantitative modeling and multi-variable analysis? That's what you need to master to be decent at salt target analytics. The variables are milk PF, cheese density, MFFB, cheese pH, brine pH, temperature, and surface-volume ratio, and likely a few other ones I'm forgetting. So there is a way to do it with math. I don't think you want to see those papers, though. If you do, I can share them with you. It's ultra geeky. Beyond that, most people honestly guess and do trial and error for a single type of cheese until they get it to a point where they like it. That's where the 3-4 hrs/lb guideline comes from. Most people who make commercially have predictable milk supplies and cheeses, so the make recipe is tuned to work for them.
