Hi Clare: I get the best results when I use "tulle" (I think that's how you spell it) on top, and then the thin water solvy on top of that. Even after you wash away the solvy the towel loops will still come up into the embroidery especially lettering. With the netting it holds down those loops better and there's no problem just trimming around the design to rid the excess of the netting.
I get my stash at the remnants box at most fabric stores for little or nothing and in many colors. Best thing about it is that you don't have to match the color exact just dark or light and you don't need much either.
Good Luck