In my experience fostering a dog generally very stressful for them at first. I fostered a Boston Terrier, and she would wet herself and shake whenever I would leave. It was awful. But as mentioned before, no drama at the door. Don't make a big deal out of leaving, or coming back, and desensitize the triggers by picking up the keys and the coat etc but not leaving. Once she realized I was always coming back, this stopped.
That was my only experience, all my puppies I have raised have been crate trained (Ian Dunbar) method, and I think that they feel very secure that they're safe/comfortable and that I will be returning. I however am never gone for longer than 6 hours, and usually just 2-4 hours at a time. They tend to get to take turns going with me places. I take them to stores, and even simple things like down to get the post.