Neal Stephenson wrote his Baroque Cycle, all 2700 pages of it, entirely by hand. He did it that way in an effort to purposely slow himself down. A lot of authors work that way exclusively.
However, for NaNoWriMo, I wouldn't recommend pen and paper unless you can write faster than you type. Doing it "the old fashioned way" is great, but the idea here is to generate a lot of content quickly. Most people can type a lot faster than they can write by hand.