Dr. Paul Auerbach discusses blisters at Medicine for the Outdoors:
If a blister is caused by pressure (ill-fitting boots), you have a couple of choices. As mentioned above, prior to actual blister formation, you can protect or pad the area. Once a blister forms, the blister site can be padded with moleskin or other adhesive foam, so that rubbing no longer occurs, the blister should be ringed with a doughnut of padding and left intact. For a better cushion, a piece of Spenco 2nd Skin (an inert gel consisting of polyethylene oxide and water) can be laid into the doughnut hole and the entire area covered with a second layer of moleskin or an absorbent bandage, such as a Spenco adhesive knit bandage.
The best treatment for blisters, as for most outdoor ills, is a healthy dose of prevention. Thorough instruction on proper footwear, socks and quickly responding to ‘hot spots’ are an important component of preparing your Scouts for a hike or backpacking trip.