The purpose of the Ultraphos is to soften the debris in the gallbladder and liver and relax the vessels (Common Bile Duct) so the debris passes smoothly. Don't want anything getting stuck in the common bile duct. Ouch!!! Don't do this flush without ultraphos.
I have never followed any pre-flush rules. I try to take my last sip of Apple cider about a half hour before I flush and I always save a little to take after the flush just to keep the common bile duct loose.
I wait at least two hours from my last meal to do the flush. I'm usually very hungry a couple of hours after the flush also and will eat sprouted grain or some good soups before I go to bed which I feel gets things back to normal quicker.
I drink distilled water all the time anyway but after the flush I drink it only when I get thirsty. Doc Sutter