Most species need a cooling period, as mentioned. Lower the temps, by say 5-10 degrees, feed less and keep the humidity lower. Obviously, this can be a stressful period for frogs, so only the healthiest animals should be subjected to it. After about 2 months, raise the temps to normal, feed heavily, and mist often. This is where the rain chamber comes in to play. Once you have regular calling from the males and females look big (like what you're describing), introduce them to the rain chamber.
Alot of times, groups or frogs get better results than a single pair, but it can happen with pairs.
Having just bred white's (which breed similarly to white lippeds), I can say from experience that you will need to provide much more food than you might think, both for the tadpoles and the froglets. You might end up with literally thousands of tadpoles if your frogs cooperate.
Also, have a several tanks ready for the tadpoles, you'll need em!
Finally, I'd like to say that I really hope you can get these guys to breed, it would be great to see more CBB white lipped TFs in the hobby.
Good Luck.