Originally Posted by
Alty
You're going to have to retrain both, since you can't be sure that only one dog is leaving a little gift behind.
Paper training is horrible, and this may be why you're having issues
Start as if they were brand new puppies. It won't take as long as training a puppy, because they both know the basics, but this is what I would suggest.
First, get a bell. Attach the bell the the door (I'm recommending this only because you stated that the one dog doesn't know how to ask to go outside). When you take the dogs out for a potty, put their paw on the bell, making it ring. Then outside, pick a potty word, I used "potty time", and when they do their business, tons of praise, a treat, and back inside.
If you catch one of them pooing then a firm no, and even if it's mid poo, pick the dog up, take it outside, use the potty word, and then praise when the dog does its business.
If you find poo in the house, but didn't see who did it, then just clean it up, and say nothing to the dogs.
Positive reinforcement, and always be present when they're out for a potty break.
The goal will be that when they need to potty, they'll ring the bell. I've never used this technique, because my dogs have always been good about telling me they need to go. But I have a neighbor, and a good friend, that both used the bell technique, and it works very well. It takes a bit of time and patience to train, but if you're consistent, they will catch on.
Do not get a doggy door. You have to be present to train them. You have to go out with them. Well, not only you, others in the house can go as well, but make sure everyone is consistent. In other words, make sure everyone does the paw on the bell (if that's what you choose to do), and make sure everyone uses the same potty word, and praises and treats.
Consistency, time, and patience. They'll get it. :)