I've used the mag citrate personally, and I'll just tell you what I did. Take it for what it is worth.
Regular day prep for flush, eating wise, veggies and fruit, no fat. 4 hours prior to bedtime, 1 oz.
of liguid mag citrate from 10 oz
bottle. (1.7 grams of mag citrate, look at the nutrition lable (top) for amounts in your particular bottle) 3 hours prior to bed, 1 oz
mag citrate in 8 oz.
water for tast only. 2 hours prior Etc. 1 hour prior etc. then bedtime, oo/gfj.. Next morning more mag citrate, x 2 then regular diet.
Got out 3 1/2 x 3/4 in. stones and lots of chaff.
It works, take the amount you feel comfortable with. Your dose on your post seems right, just give it time to work before oo/gfj.
More water seems to help with elimination, read the bottle, the one I saw at walmart had that mag citrate is used as a bowel prep for medical procedures (empty bowel procedures), and for laxative uses.
Seems that the mag citrat and ES are things that cause a draw into your bowels for water from any pace it can come from. To drink more water, I would think the elimination would be more effective.