I use the washable ones that I get at the Dollar store. Three in a pack. I have to hide them from the kids.
I have even used the colored ones. I had a purple one and was afraid that it would show through, but it didn't. Washed right out.
When doing my embroidery work. I use 6 inch squares of fabric. I hoop a sticky back film and run a thin layer of the glue stick, next to the hoop and away from the embroidery work, on the film, place my fabric down and do my machine embroidery. The glue stick helps to keep the fabric from moving so I never get puckers and my outlines are perfect, and it does not show through to the front side.
Syl
for those of you that do machine embroidery... the film I use is the same that the stucco guys use to put on their windows before they stucco so they don't have to wash windows when they're done.
It comes on a huge roll 25 inches wide. I forgot how long, but I've had it for 5 years and still have enough for another 5 years plus. $40.00 for the roll. I can't afford the price Joann's or other's charge.