We pretty much had our daughters go naked from the waist down for several days in a row, didnt leave the house, and put a portable potty pretty much in every major room of the house. They also were expected to clean up after themselves if they made a mess (that dealt nicely with the stubborness issue or the "I'm too busy to stop playing" issue) and it teaches personal responsibility for ones own actions. Our eldest was potty trained in less than a week at about two and three months of age. Our youngest learned over a single weekend at exactly two. We pretty much took the line of this is what is expected of you and we have every confidence you will succeed. They did get a sticker occasionally (intermittent reward system). Of course they have to have access to a potty during the night if they need it, so we just put one in their rooms next to the nightlight. (they had both moved to a toddler mattress on the floor by 15 months). I think so much is made out of potty training, much of it psych nonsense, so often it is the parents getting trained and jerked around. I wouldnt think the CF would make too much difference, your grandson may have to sit a little bit longer if he is a tad constipated (do watch out for a rectal prolapse in the young ones). Anyhow, best of luck, have expectations. The good news is that poo washes off : )
