What is press cloth? (this question could also be called "Have you ever used "stitch witchery"? Can you help me?)

A friend showed me how to use stitch witchery, and it was fun and easy so I bought some, but now it’s been a long time, and the directions say to cover the fabric to be stitch wicheried with “damp press cloth”, and I don’t remember using that or what it is. I tried googling without much luck. Can anyone help me out here? Can I just take any piece of fabric, make it damp, lay it over the real fabric, and get going?

Thanks!