I have nerve damage and mild fecal incontinence with no urinary problems. I can mostly manage my problem with eating habits and timing, but there are occasions where I wear a brief.
For fecal incontinence The real thick, expensive briefs aren't necessarily your best option. I find briefs like Attends poly or waistband work excellent to hold problems in. Your biggest problem with bowel problems is probably not going to be leakage but odor problems. The best thing I have found to hold the odors in is a lightweight poly brief, plenty of rash cream, and a latex cover over the brief.
The latex brief covers can be hard to find but are usually available on ebay. I can upload a picture if anybody is curious.
If you have total bowel incontinence you may want to talk to your doctor about other options.