For mixed saltwater, you should be testing specific gravity (~salinity) rather than TDS, and probably a few of the other tests that you run on your tank, such as Ca/alk/mag, maybe phosphates and nitrates if you're having problems, or super thorough
Fwiw - the slow clearing time, the gray haze, and the crazy buildup of white stuff on the inside of the mixing bucket no matter how slowly the salt was added... wound up not being worth the trouble in my case. The fish/corals didn't mind any, but I'm willing to dose a little more threepart rather than deal with scrubbing out the mixing bucket and then waiting 1-2 days for clear water every time I need to wc.
Also! in addition to what Mr. Ugly said, if you're having to keep ratcheting up the ca dosing with no apparent effect, check your magnesium! If mag is low, ca won't climb properly.