There are two kinds of "pounce" type powder. The regular pounce which is chalk. This will come off very easy while quilting and usually needs a bit of airspray to keep it from rubbing off while quilting. The second which I believe is better is the "Miracle Chalk". This is the one that can be removed with steam iron. It stays on longer and will brush off. I use this for machine quilting but as previous posts indicate has to be done a small amount at the time.
I quilt 50x60" pieces in the Baptist Fan design and will pounce across the width of the quilt. The lines will stay on enouch for me to see it. I then mark the next line. To mark with this you should just rub the pad across the stencil like you would erase the chalk off the blackboard. You don't have to pound the pad.
The Miracle Chalk only is available in white.