For shoulder mounts there's no reason to case skinthe whole animal, unless your referring to just peeling him off from the shoulder up cased.
Just cut him around behind the shoulder and around the front legs and peel him off.
Do all you prep work on hides, then tan. Dremel out nose, eye, ear area. Cut a lip slot, rough up form and when tan is ready
just pull it over like a sock and do the taxidermy work. Check reference for ear placement also.
Very simple and easy project. Tons of pics in the reference section and on the internet. Take your time on the eyes
as they will make or break the mount. Dogs are fun to work on, don't rush the project and you'll be happier in the end.
Lips should be tucked hair to hair. On the front of a dogs mouth under his nose there's a line from nose to lip, that's tucked hair to hair also,
Make a little cut channel on the form to tuck it in. The little things will make the mount respectable.
You'll find reference photos here:
http://www.taxidermy.net/forum/index.php/board,23.0.html