If you want to do a "real" long draw on a drop spindle (top or bottom whorl would both work), you'll need to start each new length ahka-style so there's no pull on the unspun fiber at the start of the draw. Once the yarn hangs together, you can "drop" the spindle and spin it normally.
That said, I've spun really fine fibers on a top-whorl spindle in the standard drop-spindle mode -- either with alot of fast inch-worming, or by having alot of twist ready to move into the unspun, drafted section so it's yarn-enough to take the weight of the spindle. It takes a fair amount of practice, though (or, it did me!)
You can also mimic a long-draw style on a drop spindle by spinning a more woolen yarn -- do not compress continuously along the length, but pinch-and-release to let twist into the unspun portion all at once, then move your pinching hand up to the unspun roving, and draft more above it before allowing twist in.
Now, there are plenty of great spindles designed for long draw spinning: the ahka, a great walking support spindle; the tahkli, a great fine-spinning support spindle; the Russian spindle, a traditional cashmere support spindle; and the Navajo spindle, a wonderful support spindle for anything from lofty singles to strong singles for Navajo plying.
I also ran across a wonderful description of Anasazi cotton spinning on a Hohokum style spindle -- this is a smaller-than-Navajo style spindle used to both spin and ply cotton.
(based on a posting by me on spindlers, this day)
