How about trying an acid reducer, like Tagamet, Pepcid, or Zantac? Some people get good relief from the butt burn by reducing stomach acid. Also, fiber supplements may help by helping to absorb the excess acid and adding bulk to the stool.

Jan

Keep a thick layer of barrier cream on at all times.  Also, have you considered a bidet? 

The only thing that came close to eliminating "butt burn" was when I took Omeprazole for an extended period of time (several months).  I was given the go ahead to take it for that long by two doctors because the suggested time frame is only several weeks.

After taking it for almost two-three weeks, for the most part I did not experience "butt burn". It worked so well that I began sleeping through the night.  Well, this led to accidents in the night because the burning sensation is what I often have when I need to wake up and go.  

I stopped taking Omeprazole earlier this year due to the nighttime issues. Since then, I've been using two different barrier creams, but yes sometimes the burning is horrible.