I do not think you/we can prepare yourself for what I experienced. I experienced severely, double severely dehydration using the Epson salt recipe through out the night and making my slight cough into something much worse then expected.
I wound up needing to drink sips of water throughout the night because I would wake up not being able to breathe otherwise. I barely got any sleep that night because of constant coughing as well. Although it turned out to be my most successful flush out of three. The hacking could have contributed to it. Who knows?
I would suggest you consider trying one of the alternatives instead of the Epson salts drinks if in doubt or weak. I personally figured I was sick anyway, likely sick from the last flush, instincts said I should not wait and persue this cleansing demon, and lastly what had I to lose? So I flushed even though I had a cold with a slight cough.