I know what you mean...I hadn't done much elastic until diaper making, even though I've sewn a lot over the years. This is what I do. I take the whole piece of elastic, i don't cut it until i'm done installing it. I tack down the end at one elastic point by setting my zigzag stitch to zero and stitching the end a few times. Then I set my machine to a regular three step zigzag. If I'm using polybraid, I usually stretch the elastic pretty much as far as it will go with my right hand. With my left hand, I guide the fabric under the presser foot and sew slowly over the stretched out elastic. I kind of have to pull the fabric as I sew, or else the zigzag will be too close together. I think that's my machine though. When I get to the end, I tack it with a few more size zero zigzags, and then cut the excess off.
Is that what you need? Or how to do hidden elastic? (which really sucks, but I do it when I make serged dipes because I think it looks nicer than elastic in the seam allowance).
