With soap, in my experience, sometimes it is more difficult to learn the nuances of each specific soap. My advice would be to add a bit of water and whip the soap for a specific amount of time. if you keep the amount of soap and time standard, you'll find the amount of water required easier to determine.
I always keep a tub of AOS non-scented shave cream around and when required I will add a tiny amount to the soap. This is an easy way to make the lather a bit thicker.

Enjoy the journey.