These scratch offs are great for classroom management. The file is also editable for you to be able to customize your rewards to meet your classroom needs.
To make the scratch off mixture: mix 2 parts metallic acrylic paint and 1 part dish soap.
I used painters tape to section off the bottom rectangle that I was going to paint. It took me 2 coats of the mixture to hide the text underneath fully. Make sure the first coat is completely dry before putting on another coat.