I think the Epsom Salt cleanse in and of itself will help your flu. One time I started to come down with the flu and I remembered doing that Sea Salt water cleanse from The Master Cleanse lemonade fast and decided to try it to see if it was the stuff in my bowels that was making me ill. Well it worked, after everything came out, my runny nose and aches went away.
That taught me the importance of keeping things moving through the bowels by eating good foods with fiber, fruits, vegetables, etc., But I don't know if the Sea Salt cleanse would cure every flu type illness though. That's just what worked for me. I wouldn't stress out about getting out the stones too fast. It's not good to force the issue (so to speak).