Don't brush off the kennel cage idea..that is what they recommend..as some said to leave the door open for them. That was their home and that is where they feel safe. My daughter has a rescue dog and he still doesn't know anything about socializing. He just stares at you if you throw a ball at him. Thankfully he has attached himself to their other dog..she helped show him how to eat and potty etc.
He is terrified of storms and tries to get as high off the ground as possible. He weighs 150 pounds so he just climbs on the couch and digs frantically or jumps on their bed and digs in the pillows. He pants and tries to hide on July 4th . I think he was left outside in storms and possible got a lightning strike on his cage or someone hit the cage and jarred him..he doesn't like the noise at all. He also eats a lot. he would eat till he throws up if he was allowed to. He also eats feces..it has to be cleaned up in the yard daily. I think that is because he was never out of the cage before and they get bored or hungry. The list goes on but as far as the cage with the door open in a quiet place is what he needs in my opinion and a few others here..they feel secure. I know many that even leave their dog in them at night time..The dogs don't seem to mind.
Watch Cesars show if it is on where you are..he does a lot of rescue work.
I'm sure you can find a lot of info on the internet.
http://voices.yahoo.com/timid-rescue-dogs-helping-them-overcome-their-timidity-2624629.html
Snoozy