Agree that yes, if it's a stencil with the mesh, you have to use the pounce. If it's a stencil where it's cut out lines, I actually prefer to use a Crayola Ultra Washable Marker now since I've never had a marker fail to wash out with warm water and soap. I have an old fashioned top loading washer though, not a newer HE one so it gets plenty of water.
I will note that it is possible to swipe too much powder on the lines. If it's on too thickly, it just cakes up into this weird powder line that bounces everywhere when you handle the quilt or when it gets stitched on. Even with the hairspray trick, if it's too thick for the hairspray to "set" it, it won't work. The Pounce is such a great idea but can be kind of finicky to work with!