I was skimming through the Thru-hikers Companion and noticed that there are a couple parks where permits are required, for example the Smokies and Shenandoah. Since the Smokies will come in the first month, it's easy to arrange for that permit before I leave, but I have no idea when I'll be reaching the Shenandoahs. Since I haven't seen much talk about this, I'm guessing people just find a computer in the towns just before the park?