Water soluble stabilizer - Mainly used when one doesn't want a permanent stabilizer left behind, or to hold down the 'fluff' on towels and fleecy fabrics when machine embroidering. It washes out. It would work for what you suggest depending on what you mark with, There are different types. But be careful, don't use felt pens or ink as the stitching will take up the inks and can't be removed.
A pounce pad can just be powdered chalk tied up in a bit of fabric, and dabbed over a stencil to leave the pattern. I have never used one, I'd rather use a sharpened chalk stick.