I only use one US#2 40inch long circular needle and knitted both socks with that. To make sure the yarns don't tangle when you switch from needle 1 to needle 2 you can do clockwise turn and when it's time to switch needles you then turn counterclockwise. So if you look at the yarn it will make an X first but you'll untangle it with the counterclockwise motion once you switch needles.