A quick search turns up a few interesting things online
http://www.electricalaudio.com/phpBB...hp?f=5&t=41372
http://soundhow.com/313/bob-dylan-ti...rding-process/
http://books.google.com/books?id=c9d...niques&f=false
http://www.jamcast.co.uk/early-recording-techniques/
http://www.kdvs.org/studioa/sixties.html
http://www.gweep.net/~rocko/sufficiency/node31.html
http://mudcat.org/thread.cfm?threadid=101857
http://www.downbeat.it/vintagerecordingtips.htm
Not folk, but of course the Beatle's recording techniques are well documented, too. I think one of the main things back then was that there was very little overdubbing, and often very little separation between instruments. Recording was done relatively "live" with a room that had a sound to it, as opposed to the later approach of very dry tracks of completely separated - usually overdubbed - tracks with reverb added later. Mics were mostly large diaphragms, or ribbons, and stereo was still something no one was sure what to do with.