At first, you should only keep him seated for a few minutes at a time, don't insist and be prepared to delay training if he shows resistance. Until he is going in the potty, you can try to empty his dirty diapers into his potty chair to help demonstrate what you want him to do.
An important part of potty training children with special needs is using the potty frequently. This usually includes 'scheduled toileting' as outlined in the book 'Toilet Training Without Tears' by Dr. Charles E. Schaefer. This 'assures that your child has frequent opportunities to use the toilet.' Sitting on the potty should occur 'at least once or twice every hour' and after you first ask, 'Do you have to go potty?' Even if he says no, unless he is totally resistant, it is a good idea to take him to the potty anyway.
If this routine is too demanding on your child, then you can take him to the potty less frequently. It can help to keep a chart or diary of when he regularly wets or soils himself so that you will know the best times to have him sit on the potty and maximize your chances that he has to go. He is also most likely to go after meals and snacks and that is a good time to take him to the potty. Frequent visits during the times that he is likely to use the potty and fewer visits to the potty at other times of the day is another good alternative. Other good techniques include modeling, where you allow your child to see family members or other children using the toilet, and using observational remarks. This involves narrating what is happening and asking questions while potty training, such as 'did you just sit on the potty?' or 'did you just poop in the potty?'
Even after he begins to use the potty, it is normal to have accidents and for him to regress or relapse at times and refuse to use the potty. Being fully potty trained, with your child recognizing when he has to go to the potty, physically goes to the bathroom and pulls down his pants, urinates or has a bowel movement in the potty, and dresses himself, can take time, sometimes up to three to six months. Having accidents or occasionally refusing to use the potty is normal and not considered resistance.
Early on in the training, resistance should be treated by just discontinuing training for a few weeks or a month and then trying again. In addition to a lot of praise and encouragement when he uses or even just sits on the potty, material rewards can be a good motivator. This can include stickers that he can use to decorate his potty chair or a small toy, snack or treat. You can also consider using a reward chart and getting a special treat if he gets so many stickers on his chart.
You can also give treats or rewards for staying dry. It can help to check to make sure he hasn't had an accident between visits to the potty. If he is dry, then getting very excited and offering praise, encouragement, and maybe even a reward, can help to reinforce his not having accidents.
Another useful technique is 'positive practice for accidents.' Dr. Schaefer describes this as what you should do when your child has an accident and wets or soils himself. This technique involves firmly telling your child what he has done, taking him to the potty where he can clean and change himself (although you will likely need to help) and then having him practice using the potty. Dr. Schaefer recommends going through the usual steps of using the potty at least five times, starting when "the child walks to the toilet, lowers his pants, briefly sits on the toilet (3-5 seconds), stands up, raises his pants, washes his hands, and then returns to the place where the accident occurred." Again, although you are trying to teach him the consequences of having an accident, this should not take the form of punishment.
While it may take some time and require a lot of patience, many children with special needs can be potty trained by the age of 3-5 years. If you continue to have problems or your child is very resistant, then consider getting professional help.
