I was asked about the water soluble stabilizer that I use for my applique. The kind I have been using is found here. It is easy to use - I just trace the shape using a pencil, then cut out, making sure to cut on the inside of the line, as the fabric takes up a bit of space when turning under, and I don't want my applique pieces to grow.... It does wash away, leaving a little bit of fiber behind that provides a tiny trapunto effect.
I have also been looking at this type , but haven't tried it yet. It is fusible, so that would help to hold it in place until the seam allowance is glued to the back side.