Congradulations on your new dog
. First of all, don't reward any of his skiddish behaviour, no telling him ooh it's okay, or anything. If he's acting skiddish, ignore him. Give him some time to adjust to his new home. Just let him be and he'll come out when he's ready. As for the leash, when he is comfortable being there, you can start putting it on him and just let him drag it around. If he likes to play then put it on him then start playing his favorite game. He'll soon learn that the leash means something really fun is going to happen and he'll begin to get happy about the leash being on him. I too rescued a border collie that was like this, it took a lot of positive training, and playing to get him out of his shell. A lot of this could just be he just needs time to adjust to his new home. As he gets more comfortable with the house, and the leash you can then begin tiing the leash to yourself so he's right by you and you can keep an eye on him. After a while, you'll begin to learn his way of letting you know he has to go outside
. Hope this helps! Good luck with him! And feel free to ask any questions you need!
~Amy~