I miss living on the AT (Appalachian Trail)! We used to do 3-4 days on the AT regularly, so much fun. I wish it was more than that, but... we lived 5 minutes away, lol.
One word about Montana with the dog, is be VERY aware of wildlife. Not so familiar with the Oregon coast, other than that it's gorgeous
I don't have any books/websites, per se, but from experience I would recommend:
-Making sure you have enough water for the dog.... know how much he drinks. We always purified our own water, but when we couldn't I planned to pack enough for two people for the dog.
-Make sure you have a dog-friendly first-aid kit.. including gas-x strips..
-Depending on the terrain...booties are your friend. Get them used to wearing them far in advance.
-Also, reflective gear beyond a backpack is key!
-Pack a long line. Even if your dog's recall is solid, it's hard to say for sure in a very foreign area with a lot of wildlife scents, distractions, etc. It's a pain in the neck while you're actually walking, but invaluable for potty time, camp time, etc.
I'm sure there's much more than this, these are just what I can think of off the top of my head