Do you have a bidet in your bathroom at home? My husband does not have IBS, but he does have a weakness in the bowel as a legacy of a severe bout of dysentery many years ago. He finds that when he's particularly bad, rinsing in the bidet is very soothing. He then pats himself dry with toilet tissue.
If you don't have a bidet, use a spray bottle of water with a fine spray. You could always carry a small spray bottle with you to use in the bathroom when you're on the move. It's a good idea to avoid soap, as this may make the area even more sore than it is now.