Do you use a foam blocking board?
If so, (and if you’re also patient!) you could conceivably block in sections. Block however much length you can fit on the board, pin, spray and tug to your heart’s content, wait till it dries and then slide the board down to the next section.
If your board is sufficiently long it may only take two or three go’s, depending on your scarf’s length of course.
I’m lazy and cheap so I don’t own a proper foam blocking board. I block scarves on my couch. (It’s pretty straight and flat on the top edge.)
I just lay it out, tug on it till I can get it pretty close to the shape I want, spritz it with water and let it dry. (I’ve never pinned one out, though I know for some yarns you’re supposed to… probably not good for the couch at any rate. :))
If your scarf is longer than your couch… well, I guess you could work that in sections, too… O.o
Oh, and an ironing board would probably be a good substitute for a couch, too. Though possibly not as long… also, an old bedspread maybe? (One you’re not afraid to pin holes in?)