I don't know if this will work, but as a young child, we would take sheets of paper and a crayon and completely mark the sheet of paper with one color (lets say used a yellow crayon and turned a piece of white paper into a piece fo yellow paper), then over the yellow markings, we'd take another crayon and color over the entire thing again, we'd do this with several different crayons, with black being the final one. theis would create "layers" of wax (or whatever crayons are made of). Then we take a penny or something and scratch through the layers of "wax" to get down to differnet colored layers. ever since i've seen scratch off lottery ticket and the orange peel style targets, it's reminded me of what we did as kids.
I've never tried this, so don't know if it would work. however if you're simply doing note cards, it shouldn't be too much of a wast of time if it doesn't work. you could borrow the kids'/grandkids' crayons and give it a shot. or heck maybe they could help you.
again, just a thought and don't have a clue how it will turn out, but good luck.
c.r.a.