Mohair doesn't have the barbs on its surface like wool fibers do; to spin it, you need to add quite a bit of twist to get it to hang together well. For this reason, it's usually spun fairly fine (so the extra twist doesn't lead to corkscrewing, but can be used by the fibers in the yarn).
Generally speaking, mohair is too "harsh" to wear against the skin. Generalizations aside, though, there are two considerations that might allow it:
(1) Kid Mohair can be quite fine
(2) some people can put a coarser wool against their skin
(3) the "irritation" can have its uses -- it is warming the skin. I think on that with my mohair scarf and the irritation becomes a blessing, on cold days
(ok, three ideas!)
It's the underlying harshness of the fiber that drives whether it can be worn next to the skin or not; granted, you can spin even merino into steel wool, but it won't irritate the skin. (I just did that, by cabling merino -- it's still lovely and next-to-the-skinnable, just not fluffy-soft any longer. Sigh. Luckily the next test worked -- 4 ply! yay. Still bouncy and soft.)
The "usual way" to get soft yarn is to spin it open and fluffy; I have some notes on that on this post along with a photo of lockspun yarn :-)
For a soft yarn, you want minimal twist to be "yarn". Also, plying helps the singles relax a bit, as twist comes out of the singles to make up the plying twist. A 2-ply takes more twist out of the singles than a similar-looking 3-ply (i.e., of the same twists-per-inch...).
Mohair will tend to "halo" once it is knitted up; my first handspun was Romney and Mohair plied together, and the winter hat looks quite "wow!" on the really dry winter days. That's it in the photo at the top, still in daily winter use.
If you have raw mohair/angora goat fiber, I'd wash it first, then try both carding and combing to see which I liked better.
Carding will give you a pouffier yarn for spinning, and with a smooth fiber like mohair, combing will give you a very smooth yarn.
Carding from just washed, flicked/opened locks is more likely to be uneven--though with an eagle eye, steady hands, and patience you can spin smooth yarns directly from the lock.
My favorite type of spinning with washed, un-processed mohair is "lock spinning" where I spin and purposely leave out the tips so they fly out of the yarn (the first half of the mohair lock is tightly spun into the yarn!) giving me great "curly" yarn.
Mohair's also terrific for boucle; the "quick-step" boucle spinning is:
- spin fine mohair singles (Z)
- spin some other fine single (mohair, wool, whatever -- or just have some commercial thread if you like) (Z, if you are spinning)
- ply the mohair onto the other single, stopping to push up the mohair to make big, sloppy loops of mohair on the other single (S)
- now re-ply this 2-ply Z (same direction as the mohair single) with a fine, commercial thread. The idea during this ply is to repeatedly "cut" the big mohair loops into little boucle-looking loops (this is boucle, after all!)
I did this in a class once, and was amazed when it actually worked - wow! So now I have 10 yards of boucle, LOL.
(from postings by me on spinning_on_the_edge, mar 2007)