Merri,
I think most of us who have been in your husband's situation have had this problem. It certainly isn't a pleasant experience and does cause considerable discomfort.
During treatment my doctors recommended taking Colace and Senokot-S a few times a day. This seemed to work most of the time for me, along with plenty of water. Other OTC products (fiber supplements, etc) did nothing.
My primary care physician recommended a herbal tea called Smooth Move. This also contained senna (which is in Senokot-S) and worked most of the time.
Certain foods tend to trigger a bowel movement and this can vary from person to person. For me greasy foods and coffee work wonders! I actually find that a breakfast from the "golden arches" fast-food chain does the trick
Yogurt with probiotics (active cultures) also helps. I would add yogurt to my smoothies, which were my primary source of nutrition during treatment.
Good luck!