I wouldn't force "socialization". Just do exposure after a two week shutdown in a new home. Don't need to force the dog to do anything.
I have no plan on forcing socialization, especially when we first bring him home. Is two weeks enough? I was planning around 4 weeks, with all of the ins and outs of his recent past. We met him for the first time last night in the fosters home and were there for about an hour. Lots of barking, wouldn't come near us in the first 20 minutes. By the end of the session he was taking food from hands but retreating to the current foster parents. That's enough progress for me on the first visit, and better than we both expected.
I feel its safe to say he will become a social dog again with enough positive training, its pretty apparent he just wasn't given much attention, or positive attention from his previous owners, but I also don't think he was severely neglected/beaten in order to be fearful of humans. He was very interactive with the foster parents, licking faces etc. And even with the young adults the foster parents have that no longer live at home, he is normal when they pop in and out of the home.
We are moving forward with the adoption, the home visit is tonight.
Oddly enough, if anyone wants to dissect this behavior; car rides with strangers is an almost instant positive socialization experience for him. When the foster parents picked him up, they spent about 2 hours trying to get him to become acquainted with no meaningful progress. The person surrendering the dog (not the owner) had the same issue picking up Guido from the owners. But said if you get in the car with him and go on a drive he relaxes and will be okay. Sure enough the foster parents got in the driver seat, Guido was put in the back by the person handling the drop off, and by the time they got home, he was fine. There was no aggressive behavior in the car, no fearful barking.
We are going to try that approach on Monday on our next visit with him.
Thank you for the responses thus far. I can do all the reading I need to on anxious training, and so far has been very educational. It's nice to be able to hear first hand experience and discuss any questions with actual people though, so thank you again for anyone willing to chime in.