[had to send 3 parts; size limit]
I think the hydration thing is overhyped -- I drink when I'm thirsty -- but it took me awhile to develop the pattern habit: shed backpack, fill Outward Hound collapsible waterbowl, carry 1-pint bottle for dog water. Dogs can't sweat; they pant and drool, may need more water than we do. I dunno. The only time I've had to wait for them is above timberline in summer sun, they wilt. I hand-feed scraped snow or make a pupsicle out of them, which they love.

Al may be a bit of a tenderfoot. He's a rocket on the paved playground, and wears his pads thin. I've seen him get really sore feet on spring snow (running, keeping up with me on Nordic skis) and loose sand (beach, roads). They're not used to loose sand. It gets between their pads and irritates the soft skin. I think dogs may get used to this if they live with it, but our do not.
I carry these "Pawz" rubber balloon booties for emergencies. Blue, medium size. I've never tried them occasionally on snow, seem to work OK, but I just want something to enable the dog to get out in an emergency. I don't see using them regularly. I might try Musher's Secret for snow someday.