I'm 3b, and when my hair was unlayered and waist-length I used to do 2- and 3-strand twists quite frequently. Like KK said, it would take for.ev.er, but the end results were always cool.
Many times I'd then put the twists up in a high bun, a high-, side- or low ponytail, or wear it half-up/half-down. With that much hair, I was always looking for variation. Sometimes I'd sit under a dryer or let the twists dry overnight and then undo them, leaving me with rope-like spirals.
Lolo, don't quote me, but I would think that a twist-out would give you a cute 3b look.