I have always chugged mine on 3 MCs (40/28/21) with no problem whatsoever.
I don't know about the difference in effectiveness but I have found the natural sundried non processed Celtic Sea Salt to be the best and certainly the most palatable. It is much less astringent than any of the white salts.
Read the FAQ advice from and Ayurvedic doctor on the SWF.
Vary the amount of salt
If you still get sick from the SWF (Salt-Water-Flush) and the lax tea is not helping you eliminate you might consider and enema. While Mr B doesn't recomend them many folks in the forums have done them with much success for getting the plumbing working and also they've done them during healing/detox crisis and have gotten instant relief.