I think your problem is that you are thinking of a "recommended amount", not that you need different products. Any alkalinity product will raise alkalinity if you add enough.
Following a manufacturing recommendation for an alkalinity dose doesn't make sense. You dose what amount is needed to maintain alkalinity, not what a manufacturer thinks might be a good dose for a reef they have never seen. You determine the dose by trial and error, raising or lowering it as needed to get to your target alkalinity. Their recommendations should just be used as a starting dose.
The only time to deviate from that is if you are dosing so much that you are getting precipitation on pumps so rapidly that they clog up quickly.
If using a two part, I'd also recommend using both parts equally unless calcium is already too high. It moves far more slowly than does alkalinity, and even if calcium is at, say 450 ppm, it isn't going to rise too much using a two part.
For example, here are my directions for my DIY two part:
Dosing Instructions
The dosing instructions are basically the same for each recipe, although any given aquarium will end up using about twice as much of recipe #2 as recipe #1 to add the same amount of calcium and alkalinity.
To initiate dosing, first adjust calcium and alkalinity to roughly their correct ranges. This may require a substantial dose of just the calcium part if calcium is low (e.g., below 380 ppm). I would suggest targeting calcium between 380 and 450 ppm, and alkalinity between 2.5 and 4 meq/L (7-11 dKH; 125-200 ppm calcium carbonate equivalents).
This calculator shows how much of what parts to add in order to boost one or both of the parameters by a certain amount:
Reef chemicals calculator
http://home.comcast.net/~jdieck1/chem_calc3.html
Then, once things seem roughly correct, select a starting daily dose for routine dosing. Here are some suggested starting doses, but the exact values do not matter much. The suggested doses apply to both recipes.
After a few days of dosing, note whether alkalinity is low, high or on target. Only bother to test alkalinity, not calcium, during this period, because it is much more sensitive than calcium to over- or underdosing. Adjust the dose up or down as necessary to increase or decrease the alkalinity.
Once you have determined the proper dose, continue it until there is a substantial reason to adjust it (such as falling alkalinity as the corals increase in size). When adjusting the dose, raise or lower both of the recipe's parts together.
Resist the temptation to keep jiggering calcium and alkalinity independently. They will need occasional corrections, but that should not be the normal course of dosing unless there are substantial outside influences, such as water changes with a salt mix that does not match the tank's parameters or an error in making the mixes.
Check alkalinity fairly frequently to make sure the dosing continues at a suitable rate. Check it maybe once a week to once a month (or less as you get more experienced with the system and the tank). Check calcium once a month to once every few months to make sure it continues on track.
Remember to add an appropriate amount of Part 3 each time you finish adding a gallon of Parts 1 and 2.
