As said before, it's not THAT complicated!
My approach is to inflate tires a bit more than I think is needed and then, based on test rides, lowering the pressure. For example, on my road bike with 23 tires, I started with 100F/110R (total weight about 175). Now I use 90-95F/100-105R. On my hybrid with 37 tires, total weight about 185, started at 55F/65R, now 45F/60R.