I am certainly not the most experienced person here; I have done a grand total of 7 flushes - both epsom & non-epsom.
Believe me, you don't need Epsom Salts . Period. If you have a tendency toward constipation, then take some mild non-epsom laxative early in the morning the day after your flush, or you could take it just before bed time the day of the flush. You don't need ANY epsom salt, ever, except to put in your warm bath. That way, it makes you feel good, not bad.
Try the coke flush instead where you take foodgrade phosphoric acid in apple juice for 3 days.
I hope that everyone here will agree with me. After epsom salt, I felt like I was ready for "davy jones' locker."