amma, she paints the pounce in the direction of the stencil? one of the reasons that i stopped using my pounce was that it got hooked on the points of the stencil and bent them upwards and ruined the outlines. this sounds much more controlled. so, just dampen the cloth, dip the foam brush and slowly paint the powder on? it sounds very slow, but worth trying.
i also wonder if you could do that one block at a time before the blocks are put together.