The best hypothermia kit and treatment is early intervention - stopping, addressing insulation, adding water and food, give the subject some rest, then move along at a slow-moderate pace, and reassess down the trail. If you don't catch it early, break out sleeping bags, shelter, and assign some tasks, such as boiling hot liquid and prepping a bit of food, while more experienced adult leaders and Scouts see to getting their friend out of wet clothes, into dry if possible, and wrapping them up, one sleeping bag inside another, burrito style. Insulation will rapidly warm their core, and the subject should begin to revive... When they know what to do, they carry that knowledge with them forever, and can even improvise for self-treatment if out hiking alone.