Although I think this should be a standard procedure even if not dosing, there's a procedure I think it prudent to follow, and to help minimize the affects of WC's on dosing.
First, if you're not using the entire package, would be to thoroughly mix the salt mix to make sure there was no elemental stratification that may have occurred during shipping, and you're getting the proper proportions of all the elements, i.e. Ca, Mg, Alk, etc., with each measure of salt mix when you make up your WC water.
Secondly, following proper mixing procedures, i.e using RO/DI water, adding the salt mix to the water, etc., I would make sure to accurately get the SG you want, I preferred 1.026(35ppt), using a properly calibrated measuring device, i.e. refractometer calibrated with a 35ppt solution(not plain water), to ensure the same amount of these elements with each WC. Using a swing arm type of hydrometer, or other non/mis calibrated device can cause differences in your SG when you make up your WC water, and further skew a dosing schedule. Using a decent set of test kits, i.e. Salifert, Red Sea Pro, etc., measure your Mg first, making sure its between 1200-1400ppm, then your Alk and Ca.
Next, I would set and keep a schedule of WC's in terms of both frequency, i.e. weekly, bi monthly, monthly, etc. and volume, i.e. 10%, 15%, 10 gal.,15 gal., etc. to help minimize any skewing that may normally occur, since this is where you're adding/replenishing those elements in an ongoing basis.
Once you have your SG corrected(if needed), adjusted your parameters, i.e. Ca, Mg and Alk(individually if necessary), and your WC schedule adopted, start to measure and record your demand over a few days. Use
this calculator, fill in the blanks for your system, and select the appropriate supplement from the drop down menu's to get your dose.
Depending on a particular load in any system, it's likely that you may need to adjust your dosing based on a particular WC schedule, i.e. the disproportionate use of Alk vs Ca supplement, since the WC is better at keeping up with the Ca needs. You may notice that, with regular WC's, you may never/only occasionally, have to dose any Mg, since there is very little of it used(about 1/10th of your Ca use), and its replenished with regular WC's.
