The problem with all of these resources remains: they tell you how much CO2 your added sugar will generate. They do not account for how much CO2 the beer already contains, nor how much fermentable sugar it contains. Both of these must be ascertained before you know how much CO2 you still want to generate, so you can then determine how much added sugar is needed. Any calculator claiming to account for these factors is disingenuously making wild guesses, as these cannot be known absent actual measurements. Novice brewers would like to believe that there must be simple instructions to follow to obtain the desired result throughout the process. Slightly less novice brewers see a maelstrom of complex scientific principles which all must be taken into account every step of the way. Advanced brewers have intuited enough to triage all of this, finesse things by instinct, employee few hacks, and get the desired result every time. The guys at Budweiser aren't reinventing the wheel every day, they follow well evolved procedures. Like Dave and Kevin know 2 tablespoons a gallon works for both of them. But you will have to discover what works for you, because you are not them doing things as they do.