A gamble, but it worked - a step-by-step.

Step one: I arranged orange pieces of w/c paper where I wanted the 'sparkles' to end up.

I laid 'frog tape' over all the stencils and on gaps in between: I can be pretty messy.  In the past I've had problems finding my pencilled design when I was ready to cut through the tape. This time, instead of tracing with a pencil around each little shape, I decided to try just leaving them there under the tape to be cut out in the next step.

I used a sharp blade to cut through the tape, keeping the blade tightly against the w/c paper stencil which I had left beneath. This seemed to help me quite a lot in keeping the cuts very straight and the corners sharp.  I don't know if it would have helped as much for curves, I'll have to do an experiment along those lines.

I used an embosser along the edge of each cut - I could see the tape darken as the seal improved.

Ready to start the scrub. Looks pretty messy, huh?

I used small cubes of magic eraser to lightly scrub (wipe) off the dark paint.  I tried not to use too much water, and I blotted frequently with a tissue held ready in my other hand. I changed to  new pieces of the eraser frequently.

I think the little white places came pretty clean and with nice sharp edges - well,  most of them (one of them got too wet and the water bled under the tape).   I then painted them with the bright orange I wanted to carry around the page.  I'll post the finished painting tomorrow.  I'm glad I took the chance on this one, it really did need that additional sparkle.