Tips of housebreaking a mini bull terrier.?

I have experience with dogs and have raised a rottweiler and lab from puppyhood until old age and have never experience any issues with housebreaking - it was almost too easy. That is until my miniature bull terrier. He comes from a good line and was flown in from poland a few weeks ago - he's adjusted very well. In typical bull terrier fashion, he's quite stubborn and is pretty difficult to get his attention on me when I'm trying to work on commands but my main challenge is the housebreaking. Ill spend half an hour outside with no luck and as soon as we get inside, he'll go on the floor - carpet, tiles, the couch - he has no preference, just as long as its indoors. I am crate training him and he is also more of challenge in the crate - but he's getting better with It. I'm just looking for any tips that would work better with this breed. Currently, if I see him about to go, I say STOP loudly and firmly and pick him up and take him out immediately. This is what I used to do with other pups and when they would go outside I would praise. Problem with him is - he seems to be able to wait me out. 30-40 min outside and he won't finish his business. It's frustrating.