I would suggest using a kitchen scale to weight the food (minus the container weight) and then add in the 3% of salt (or whatever percent you want). Using the scale made all the difference for me with getting the consistency and flavor. good luck!
Two of my most used and most useful kitchen tools are a Thermapen and a digital scale. Just being able to measure accurately makes all of the difference in cooking just about anything. A cup of flour or a teaspoon of salt can weigh very differently depending on how tightly packed or how fine the grain is, better to be exact and not risk screwing everything up.
I love Thermapens! I've been looking for an equally well built kitchen scale. Have any recommendations?
The 0.1g-precision Bluetooth scales used for coffee are decent. They all seem to share essentially the same firmware, which suggests that they come from the same ODM, and they’re decent — mostly work, only a little flakey.