I went into my local Bernina store last year with one of my chenille scarves asking if there was a foot for my machine for couching - lo and behold there was this great foot. First I pull the yarn to be couched through the foot, then I close the top of it. Boy, does this ever make the job easy......not that it was hard before but this is really easy. Below is a picture of the yarn in the picture above being couched on the scarf.
Of course, the yarn I was using for the scarf below has big nubs in it (not showing in this picture) so they won't fit through the cool foot above so I went back to my regular foot.
Right now these two scarves along with the clasped weft one are soaking in the sink, will hang them to dry soon. When the chenille dries it's as stiff as a board and still pretty flat looking but after I put it in the dryer on fluff for 15 minutes they'll be full, soft and drapey....actually pretty yummy feeling.