I have used the punk wood char, and it works very well. I sort of slice off thin laths of it, probably around an eighth of an inch, put it in a small tin with a lid (which also transports it), and either put it in the oven, on the grill, or in or under the coals of a fire. It's guesswork as to when it's done, and it won't all be done evenly, but it makes a good tinder: takes the spark off a steel well, keeps it going, and is awfully hard to extinguish if it's good char. Another tinder is the hoof-type "tinder fungus" off alders and birches; that also can be charred to improve it. There are all sort of good plant tinders: milkweed, thistle, goldenrod, cottonwood down (sycamore down goes up too quick), cottonwood inner bark, and the inner bark of the junipers and other things we call cedar here, and of course the bark of some birches, are all good in their season.