I bought a ball winder for $20 from Knit Picks, but I had a hard time shelling out another $65 (on sale) for the swift, BUT I came across an awesome solution. Try Tinker Toys! I bought a canister off of ebay for about $18, I think. My can didn't have exactly the same pieces as the tutorial, but it works great with my mods. I think mine works better with the mods, even. http://www.folkcatart.com/blogs/jen/?p=742
I think if you don't use something in place of a real swift you might have problems. I wouldn't recommend doing it by yourself. Have one person crank the winder and one control the yarn coming off the hank. Otherwise, your tension on the ball winder may be uneven.