I've used the wash-away paper and was pretty unhappy with the results.
You can wash it out, but it's a gooy,gluey mess and you have to soak it quite awhile before it's gone, wrong side down in the tub or basin so the glue will sink to the bottom. Then, check the seams for excess glue residue. What it really is, is a very thin sheet of glue. If any of you try it and have better results, please let me know how. I used it for a paper-piecing quilt top (which I'm quilting right now :) Oh Happy Day!)