What's the best training approach to take with this dog?

Temperament is gentic and poor temperaments can not be changed but behavior can be modified. I had a dog who refused to come out of his crate for 3 mos at his first foster home then when out hid in a bush for days. They left him alone to "feel safe" and let him take his time. Since they couldn't do anything with him I got him. He had been crated 23/7 and has a PM background so is poorly bred. I let him go in the crate and called him, when he refused to come I pulled him out into my lap then praised him, let him dart into his crate and repeated until he zoomed out of his crate first call no pulling. He started obed cl 2 days later and graduated first with a perfect score because I refused to pander to his fears and made him obey. If he moved on a Sit/Stay cuz someone walked by he was corrected until he realized he had better do as told. He quickly learned that I was Alpha and Alphas make the decisions not him. Dogs are quick to use "terror" as a reason not to obey, look at thunder shy dogs, people make them worse by going "Oh poor baby, it is alright" thus praising the dog for being afraid. He will never be social but is fine to take to the vet and I used to have other people walk him w/o any problems.