
Would they be offended if you bought or suggested a book for them?
"Who said it would be easy.. or straightforward, or cheap?" by Alison Rowbotham (An honest guide to choosing and living with a second-hand dog) is a lovely litle book, I have a copy, and one thing it does go into great detail is separation anxiety which is all too common in rescues, and step-by-step ways to work through it.
It's the red booklet towards the bottom of this page:
http://www.apbc.org.uk/shop/dog