Take the basket out of the salad spinner and use it to trace a circle onto a stack of paper to cut out small circles that will fit into the inside of the spinner.
Place a piece of paper inside the salad spinner and have your child help drop a few globs of paint on top of the paper. The less of a consistent pattern the better!
Place the lid on and have your child give it a fast spin! (They'll love this part)
Open the lid and take a look inside at your pretty spin art design! Carefully pull out the paper and let it dry
After a few rounds the outside bowl will be a mess (but a pretty rainbow mess!). I had washable paint so it was a cinch to clean up everything. Everything came out quickly with a little soap and water.