Hey Estelle
I was watching a Fons and Porter quilting show last weekend and they had a machine quilter on showing various techniques.
She used the chalk powder for stencils. The big difference was she didn't pounce the chalk.
She put a small amount of the powered chalk in a lid like one from a coffee can, she then dipped a foam brush in the chalk, wiped off the excess then proceeded to "paint" the chalk all over the stencil. The big advantage was the chalk powder was not flying all over the place.
She made her own stencils.
I've used the press n seal freezer paper. It comes off a lot easier and less picking of the stitches to remove all the press n seal.
If you make your own stencils use the painters blue painters tape to keep the stencil in place. It peels off a lot easier than regular masking tape.
Hope this helps
Kate T. South Mississippi