What worked for Honey's separation anxiety (only when Hershey wasn't home) was the original ThunderShirt concept (called an anxiety wrap). We also used a pheromone product (wall plug-in....very oily/messy....I'd recommend the collar version) where she slept. That was D.A.P....they still make it but I understand it's a different company and reviews are mixed. The anxiety wrap made a huge difference, though.
I never had any real success with behavioral training. The dogs were supposedly already used to being separated for walks when Honey changed.