Hi Dopeysgirl,
I'm not sure if your questions have been answered, but I use a different method of ruffling without dental floss or a ruffling foot.
With your zig zag pressor foot on your machine, place the piece to be ruffled under the foot, and put the foot down. ( as if you were going to sew)
By hand turn the sewing wheel (that thing on the right side of the machine) just one turn. You should have the bobbin thread poking through the stitch you just made. Pull the bobbin thread out through the fabric. (If doesn't work, try these steps again)
Now you have the bobbin thread and the top sewing thread together pull the two threads.
Pull the threads as long as the piece of fabric to be gathered. If the piece to be gathered is unusually long, you can do this in multi areas. (the easiest place would be to start and stop at the seams)
Set the machine to the largest stitch as well as the widest zig zag stitch that you have.
Use the zig zag stitch on top of the two threads. Sewing all the way to the end of the piece that you want gathered.
Pull the threads slightly while sewing, and your fabric will gather up on its own, you can adjust the amount of gathering when you are finishing your garment.
Seam allowances
Before I had my serger, I used to double stitch my seams. First I would sew the normal seam allowance, and then I would sew another seam 1/4 inch away from the original seam and trim the seams close to the second seam.
This kept the seams from unraveling, and was easier than using the pinking shears.
I hope this helped.
Marianne