I think it is pretty easy to hit a specific amount of carbs or whatever macronutrient you have.
It requires some time and effort though. What you need to do is weigh the food or measure out everything. So if you know that cottage cheese has 15g P, 2g of Fat, and 6 g of carbs per cup, you just measure out the unit, and count the macros. Record them in a book and keep track of the book all day.
Read the labels and keep a count to determine what you can and can’t eat.
The other thing that helps is to know what foods contain what. It may require you eating very repitiously, but once you know what food combos give the right macro breaks for massive eating style, it becomes much easier to hit the daily limit.
So with a little due diligence one can hit the goals within +/- 15 cals of the guidelines.
To recap…get food guide, read labels to determine macros and calories, weigh and measure, and muck down.