Personally, I’m very fond of Wilderness Navigation by Bob and Mike Burns, published by The Mountaineers, for teaching instructors and adults advanced skills. The “Navigation” chapter of the scout handbook is pretty complete for basic skills.
I advise our Navigation Instructor, and we use a combination of USGS 7.5’ topos, custom maps, and other commercial maps to teach the scouts navigation. I have a variety of baseplate compasses from Silva, Brunton and Suunto that are used for initial instruction, assuming the scouts haven’t yet purchased their own.
Typically, for distance traveled I have taught a variation of Ranger beads (pace counting) for tracking distance covered. I don’t know that anyone in our unit besides me actually uses it, though. I’ve also taught the string method for measuring distance on a map, but largely recommend and use estimating to track it in the field. I also carry a GPS unit, but it’s largely for convenience rather than distance tracking. It’s pretty quick to pull UTM off of a map, rather than having to triangulate every time there isn’t an obvious geographical reference feature.