Its nice to hear your concern over this young man. This problem probably got overlooked over the years, caregivers not wanting to question the way it was ? or i really don't know for sure, but have worked as a caregiver my whole life. I would think, if you could get them normal, he would have better control over them. if its not because of a medical problem, then start by keeping track of them. when i worked in ecu, we recorded bowel movements regularly. !st day gave prune juice, 2nd day laxative, 3rd day enema. A lot of times, the patients had small amounts of bowel movements constantly,like you were saying( we call it smearing) but never a good full one (i know sounds gross) . Most likely because of using depends/pullups, or bedpans. not being able to regularly to sit on toilet, i think makes things a little slow and lazy inside....
anyways, i would attempt to get him to try using the toilet consistently. try the fibre or bran (you can mix bran with tomato juice makes it drinkable) and/or the prune juice. and just get him to have a good bowel movement. sit him on the toilet with a coffee, for awhile that can help. probably no one has taken the time to make it a priority, hope this is of some help to you Good Luck!
Well, it sounds like his diet is poor. If they can get him to eat more veggies that would help. But in addition I would see if they or you can give him metamucil daily. I had messy stools even though I have a good diet and this helped incredibly for me. so it may help and it tastes good. I glass a day with a heaping teaspoon of the orange flavored metamucil may do the job. My friend told me about this and it is great. Is he diabetic as this one has sugar in it. If so they may have one with a sugar substitute.