I did my first flush without water and got unbearable headaches. On subsequent flushes I drank water up until about 15 min before 8:00pm so that I had a 2 hrs 15 min before the oil. I also didn't drink within 15 mins on either side of Epsom Salts . Other than that I tried to drink as much fluid as possible through out the day as I find a have a lot less toxic reaction when my body has some water to carry the toxins away.
Good luck whatever you try.