I use it for Invisible Machine Applique. Regular cotton thread in the bobbin, invisible thread on top, blind hem stitch adjusted to take just a wee 'bite' into the applique piece while stitched right next to it. The stitches will look something like ---^---^---^
I've been happy with YLI monofil. thread and more recently a polyester thread. Good results with both.
Good luck!
Donna Mc