For turning long slender spindles or finials you need to support the end from whipping around as it gets longer. To do this I made some steady rests that use string to hold the work centered. I have tried a couple of different designs but this one seems to work best because I can still get the tool rest up close enough to turn the spindle. On these top pictures I have them on backwards to get the string closer to the work, the banjo is in the way to slide them closer the right direction. So far this is working real good for me, I guess until I come up with another idea to try.
The string is tied to the bottom left nail, then just wrap around the top right nail, and back to bottom left. Then cross over to bottom right, up to top left and back to bottom right. Then I used a standard office paper clip to hold the end of the string tight.
I have a block of wood on the bottom that will fit between the ways on the lathe bed. Then turn it and it can be held in place but just tightening the wing nut. Notice that the base of the jig is the same width as the lathe bed which helps center the jig. PDF file of the jig for 1236 lathe. PDF file for the Jet 1642 lathe.