Here is a picture of when I am adding a new strip and when I start a new length of clothesline rope. Just overlap the rope slightly. You don't want a bunch of extra bulk there.
I always have one in progress. I put a pin through at each point when I change strips. I don't leave it when I am adding a new rope because it is really fragile at that point. When I am changing fabric I just put the pin through it and leave it until I am ready to sew again.
I think it grows pretty fast. But I suppose that is relative. Probably too big for Barbie. lol
This is regular cotton fabric. It is the leftovers from straightening my edges when I strip piece.
I use regular thread. I have an embroidery machine so I end up with ends of spools that wouldn't finish another project. I'm too cheap to throw it away. I use whatever thread I have.
I hope this helps. Feel free to ask more.