"The cream cheese helped him to learn that he should ring the bell: i.e. it gave him the motivation to do it.This method worked for us"
Very good point. Part of the training needs to be to teach the dog to ring the bell. There is no reason for the dog to leap to the conclusion because human rings bell before going out. If i ring bell human will let me out. First step in the process need to be teach the dog to ring bell.
Don;t even need to associate the going out with the bell ringing at first just need to establish the bell ringing. One way is again any food stuff that will stick to the bell, cream cheese, peanut butter, cheez whiz something the dog likes.
dog licks- bell rings reward with a different treat hopefully an even better treat. repeat. When you thing the dog might ring the bell on his own with out the lure of the food stuff stuck on the bell try and see if does. if The dog does ring the bell give it a jackpot, multiple treats. If not continue to lure. It will take some dog longer than others but they will get it.
When the dog is consitently ringing the bell for food treats now you can change the reward for ring the bell to going out. Dog rings the bell his reward is going out side. voila. if he potties reward that behavior.
so the basic steps are
1. train the dog to ring bell. Use what ever means necessary.
2. one the dog know the bell ringing behavior you can change the reward for the behavior to going out side.
Trying to train the whole behavior all at once in the training slang is known as "lumping" generally not a good thing. Behaviors are more easily learned by breaking them down into smaller steps and building on those step till you get the final behavior. Sort of like trying to scale a 10 foot wall You can train and train and develop your high jumping skill but success is not likely. If however you grab a shovel and start building step you will eventual get over the wall much faster. Even though in the beginning progress may look like it is going slower.
House Training: Ring My Bell!
a training article with even more intermediate steps. Lots of small steps but always progressing is often faster than trying to take giant steps and often running into road blocks. If the dog stops progressing take a step back and see if there is no a way to a one or more intermeadiate step to the training making it easier for the dog to succeed. It is much easier to learn by being rewarded for doing the right thing. You know what to do again rather than punish a dog for the wrong. While it may never do that wrong thing ever again there are only billions of other behaviors that will have to be eliminated also before the dog happens on the correct one.