In Sheep's Clothing in the National Library of Scotland Scottish Screen Archives is a good short documentary from the 1930s about sheep, fibre prep, handspinning, and knitting Fair Isle sweaters. http://ssa.nls.uk/film.cfm?fid=1129 Ran across the link on Ravelry.
A Crofter's Life in Shetland, http://ssa.nls.uk/film.cfm?fid=0981, by the same filmmaker, is also interesting. It has more about life generally but it shows some aspects of Shetland knitting the other film doesn't, such as lace shawls.
I noticed that the handspinners in both films do not sit and face their castle-style spinning wheels directly like everyone I see with a treadle-powered wheel today, they sit at an angle to do long draw. Their position is something like what's used with a (hand-powered) great wheel, which also takes long draw; the left arm makes a sweeping motion.
I liked watching them card rolags, the women are skilled and quick.
Noticed that the lazy Kate had five bobbins on it, though they only show plying from two. Five bobbins would give gansey yarn good for knitted cables.
The rooed wool from one sheep gets twisted together roughly into a bundle about a meter (about a yard) long and folded like a skein or strick so it holds together. I noticed the same technique used in Asia on rooed cashmere fibre collected for the Scottish export market in the promotional film Cashmere is Scottish, http://ssa.nls.uk/film.cfm?fid=0578.