Hi J, congratulations and thank you for fostering! Such fun! Setting up a consistent daily routine, and obedience training can really help. It helps to eliminate some of the unexpected for him and sets boundaries and clear roles; helping him to feel more secure. He will use up energy and relax more with training sessions and anticipated daily events such as meals, walks, play, etc.
Some of Cesar Millan's ideas about incorporating another calmer and more stable dog can work well. Maybe you can walk them together (Dog#1's leash goes on first). We have had success with our little senior dog (Pennie) that was NOT used to a leash, by walking backward and congratulating her as we looked at her and praised her for every step she took. Even squatting and reeling her in gently towards me, along with anticipated praise and petting once she arrived, worked! She walks wonderfully now. While we generally use a 6ft leash for walking we used a 10-foot leash for this exercise. This was done in the safety of a fenced-in area. Another option if you can not get him to walk yet-is to pick him up and carry him to the farthest end of the yard and start walking him towards the house from there. He is walking and therefor he gets praise and is getting used to the leash and collar at the same time.
Walking-trotting is very good- the opposite way a dog is looking, without alerting them that you are about to walk, is a great way to get a dog to learn to focus on you and to get moving as well. This is done with a slack line/leash, not a taut one. It creates a little abrupt jolt that works wonders. (We agree not leaving him unattended is very wise).
Possibly just having a set time for just the two of you in an office or while doing laundry every day (=routine) can get him used to you. Just going about doing your chores/work without engaging him-hopefully he would eventually seek this out-allows him to see you without having to interact. He can learn a lot about you that way.
We are grateful on his behalf for your efforts and willingness. Thank you! Sarah
#FosteringaPet