I used to suffer from the same issue. I switched to the "BRAT" diet for about a week and it went away.
I had been without this symptom for nearly 15 years and then was in a work accident.
The added stress on my body from the accident caused anal leakage again on and off for about a year. I also found that I seemed to have become lactose intolerant and had to cut out dairy completely.
Now that the accident pain is being managed properly I can eat dairy, to an extent, and have no issues.
I don't know if any of this will help you but that was my experience. The more stress the more frequent the leakage.
There isn't too much talk of mucus secretion as a result of IBS on this or any forum on the subject. This is probably the worst part of my IBS-D symptoms (which I should feel luck about after reading other posts). I haven't found the link for this dampness yet but trying hard to figure it out. It seems to shut on and off at random times. Touch wood - 2 weeks of dry shorts. Good luck!