I have to tell you the best advice I've ever received here in the Liver Flush Forum (and I've received a lot):
"When you wake up in the morning, before you drink the 6 AM Epsom Salts drink, apply vaseline liberally to your butt. You will not regret it."
Hehe. Believe it or not, after you've done a few more, you won't feel it at all. I was told that and never believed it, but it's true. You could use A & D ointment, desenex, coconut oil, or any soothing lubricant. It's such a help.