Rescue dogs

Question
I recently rescued two dogs from a shelter rather than getting a young puppy. These are Australian Shepherds and probably a year old. They were not there very long, but when brought to me, were scared to death of humans, but not other dogs from their behavior towards my other dogs. One of them has decided to come to me some, and yesterday licked my hand. I train horses and know what each behavior represents, but realized that I've never had a dog that I didn't get as a puppy, so I do not know what some signs are. I assumed the licking was a sign of acceptance. The one that will come to me some and lick me kind of runs around with his butt to me like he might want to play but I've not tried to be aggressive with them at all. I threw a ball for my other dog, he jumped like he wanted to get it, then went back to the other dog like he thought he would get in trouble. The other dog stays pretty much wrapped up in a ball. I can walk to him without him trembling, and I can pet him, but he will not sniff of me or anything. I have always had cow dogs of some sort and know they love lots of exercise and play, but do not know what to do next to help these guys. I just go in the yard, sit down and talk quiet and friendly to them and pet them. I haven't allowed any other humans to be near them yet, only my husband, me and one other dog. Where do I go from here?

Answer
My guess is that they may have been quite under-socialized to people, but it's good that they aren't being aggressive in any way.  If you expose them to others, be sure that no one reaches for them, or intrudes on their space.  Rather, allow the dogs to come out on their own, as they did with you.  The lip licking behavior, coupled with the butt nudge, is indicative that the dog likes you and is accepting of you to some extent.  You are doing the right thing by establishing a bond of trust.  I like the first lesson for a shy dog to be "attention".  There's a great protocol for teaching it on www.clickerlessons.com, although you don't need to use a click if your dog is fearful of noise, instead just use your voice.  Once you can get them to look at you when you cue them, you can start training other behavior, and you can use the "attention" cue to divert their attention away from scary things and back to you, which will increase their confidence that you will protect them.