This was a fun last day project I did with Grades 4,5 and 6 classes. I bought a bunch of packs of these scratch art papers from Dollarama. They had three or four different colours, like rainbow, purple holographic and gold holographic.
I cut pieces of white paper to match the size of the scratch paper. Students planned their designs on the white paper, taped it to the scratch paper and traced over the pencil lines with a ball point pen.
Then they used bamboo sticks to scratch away their designs. The whole project took about 40 minutes but double that would be more ideal.