Aww gezzz ... first Lindar51 outlined it pretty well. And she also listed the least effective" but most likely option for "most" owners struggling with this issue ... go to the vet and get a "Pill" to "Fix" my dog.
Unless the dog is a rescue ... then the owner ... created this problem?? "If" that is the case ... they have had the dog since "puppyhood" then there is a lot they need to know.
Lesson one ... would be ... "Crate Train" your dog. If one starts with a "puppy" then "Crate" Training is an option. If one has a dog with "issues" whatever they maybe ... then "Crate Training" is a necessity.
But the thing is "you" don't need to know that ... your friend does ... and they are not "here." So you know ... what you are "trying" to do is "extremely difficult."
Top level pros and we have them on the GSDForums and one or two here also. But ... they have "friends" with badly behaved dogs ... and certainly ... friends of mine with "seriously" badly behaved dogs ... should at least be able to walk them properly? But they "don't ask for my help" and I don't offer. It's just the way it is. But I don't know maybe your friend is different??
If they "actually" want to fix" this ... they can do it themselves (I belive) but it would take a lot of effort. None of it "difficult" per say but yes ... a lot of work to be done. The incessant barking for one ... that needs to be stopped "Cold!" leash corrections if the owner is on sight or a proper "Bark Collar if the dog does it all the time. And a proper bark collar looks like this ...
Leerburg | Dogtra IQ No Bark Collar
Not the Citronella crap, the scent lingers (for the dog) long after it goes off and the dog does not make/keep the association with "barking???". So by and large your best options to help them ... would be to get them "here" or failing that ... suggest a "proper" Board and Train facility.
Aww well ... a lot of "background" info ... I tend to do that but ..."you" need to know that what you are "trying to do" convince someone that they should ... "Do this" to fix their dog. Is extremely difficult can't help people if they don't want help.
But to answer your question directly ... getting it done properly fixing SA would look like this.:
http://www.boxerforums.com/behavioral-issues/181570-separation-anxiety-shut-up-dog.html
Not much in the way of input on here?? But on the Germanshepardforum ... that "Pro" I mentioned (that would be Baillif) ... is here. :
Separation anxiety = Shut Up Dog!!! - German Shepherd Dog Forums
So yes as you see ... it's a lot of "stuff" the best thing you could do to actually help them is to get them "here" first as I see it.
