While your waiting for a proffesional trainer.Sit in the living room,treats in one hand, dummy in the other.Dog in front of you.Get the dog to hold the dummy and then exchange for a treat.Even if the dog has the dummy for one second in its mouth give it a treat.Just do a few mins everyday and work on duration.Don,t react or get cross in any way.Once you are both confident ,take the dog out side and keep him on a lead and do the same.See if he will walk by your side with the dummy in his mouth and always reward with food when he gives it to you.This will take about 2 weeks to get to this level.