Here’s a fun one for summer, and older preschoolers might not even get that messy. Roll painty balls down the slide! Of course, if you don’t want your slide to be painty afterward, make sure you cover it with paper. This paper makes a great background for displaying children’s art inside once it’s dry.
In this picture you can’t really see what’s at the top, but there are several containers with paint them. We put bins at the bottom of the slides so that the balls wouldn’t get covered in mulch and would be easy to collect.
For cleanup, use the hose. If your kids are in bathing suits they can go down the slide with the water, cleaning the slide and having fun at the same time.
Alternatively, you can let kids do the painting AS they slide. They can dip their hands in paint or use sponges. I probably wouldn’t use paint brushes because, well, somebody could poke their eye out. That wouldn’t be pretty! If the kids do the sliding and painting they will be gloriously messy. Have a hose or other water toy handy for washing off and lots of towels.