This might be a very late reply.........
.....We have had several newf rescues
Our most recent one is five weeks ago. After our previous rescue had to be put down after his third stroke (atavar).
Initially they, like all rescues, take some retraining and care. Especially our last rescue. She was totally out of control. But we have found that with firm rules and gentle kindness they are easy to train. Because you have had danes, you would be used to handling big dogs. Zack was considered aggresive when he came to us. But we did a round of(six weeks) obedience training with him and found that he was just un-trained. He did have a growly friendly greeting, which strangers found a bit difficult to accept, but no aggresion. Annabelle our most recent dog is just a bit of a hooligan. And she was also very timid, because she has quite a bit of trauma in her past. But we have been to a Special dog trainer with her, and he has made her more confident. He initially put her in her discomfort zones and made her realise it was not bad at all. She is now very friendly. We go to dog training every week and meet and greet everyone. We visit pet stores, sothat we can socialise and try to go walking in areas where there are a lot of people. All our newfs have adored children and seem to have a special affinity to handicapped people. I think that you need patience and tolerance, but at the same time have to be firm. Because when it comes down to it all they were bred to be people rescue dogs. And just like sheep dog always has that little bit of chase in them and a retriever always (nearly)retieves. The newf seems to have an affinity to people ;DAnd once they trust you, you will have an adoring companion for their life, which sadly is not long enough