In spite of the name, BBB is an approach, and not 3 chemicals.

A core element of the approach is accurate testing. In particular, it requires accurately testing CYA (stabilizer) levels, and adjusting chlorine levels accordingly. The "Best Guess" page explains how and why.

Another element is using chlorine chemical side effects beneficially. For example, when your pH is too high, and your CYA is too low, dichlor is ideal. But, if your CYA is high, and your pH is low . . . you'd better use another chlorine source.

But all this requires actually knowing what your pool water levels are. 'Guess-strips' are not very accurate, and never reliable. Pool stores are slightly more accurate, but equally unreliable. We receive almost daily reports of bogus pool store test results.

One of the facts the Pool Chart aggregate data is making clear is that, as hard as we push better test kits, we don't push them hard enough. The relationship between inadequate testing and persistent pool problems is very strong. You ask how you can know how much of each chemical to add, to get a specific ppm level. The more important question is, how do you know what you need to add?

And the answer to that question, is to use a good test kit.