Agreed with MRL, to help Shelby become a more confident, outgoing pup in new places and with new people, you just HAVE to make the effort to take him out and get him used to being out of his comfort zone.
I live in the coutry too, but I make put in the extra effort to take my pup into town and just walk around new places. We went to a ski hill and sat at the base of the hills and watched the kids on skis and snowboards lining up for the ski lift, (lol, I have to drive INTO town to get to a ski hill), lots of different strip malls where we up and down and up and down the strip, a horse club and met lots and lots of horses in paddocks and being walked around by owners, down-town and dealt with the hub-bub of traffic, audio walk signals, and crowds, and I just drive out to "normal" residential areas and walk on sidewalks with curbs (real novelty for my country dogs!).
Took him to work after hours, and had Falkor experience grated platforms, full-story stair, offices, hangars, helicopters, flag poles with flapping flags, etc, just to give you a few ideas of some things you can do.
Socializing doesn't mean he has to interact with people and other dogs, just be exposed to a lot of new situations.
Make a plan, and act on it! For Shelby's sake. And you want to know cold? Dark? Winter? See my location, so no excuses, young lady! And I have a minor disability, and it takes many times the effort from my part to go out and do stuff, but I do. Not to give you a hard time, but to inspire you, if I can do it, so can you! Now GO!!!