I have knocked on doors (in my neophyte days when I used to make mistakes like running out of water), and amazing hospitality has been my experience, too. Church buildings and Post Offices usually have an outdoor spigot, and you're welcome there most of the time. Empty one or two-liter Gatorade or soda bottles are a convenient and disposable temporary way to carry more water, and they're usually available whenever you need them along any roadside. Sometimes you get lucky and find one with a squirt cap. Some one-liter sizes even fit tightly into a standard water bottle cage.

When I expect to camp on snow or very cold ground, I carry a full-length piece of Reflectix duct insulation and put it under my regular 1/2 length CCF pad. If you're lucky you can scrounge a short piece from a heating contractor, or share a roll with several winter-camping friends.

Smartwool is the way to go. Carry two extra bread bags ('Bagtex') to wear over the socks for really wet, cold conditions. But don't overdo the plastic bags or you'll macerate your skin.