My students were lucky enough to have a visit from a Philly muralist and street artist (and Kaleidoscope parent!) SEPER.
We looked at some slides of his work, mused about the tools and techniques he might use, and watched a time lapse video of one of his murals going up. The kids were so stoked to learn that we'd not only be meeting the artist, but we'd also be collaborating with him that very day.
Anthony set up a demo outside, and taught us the tricks of the trade. After watching him put down the first layer, the kids got to take turns trying out spraypaint for the first time.
A quick aside: I found these awesome, tiny cans of MTN water based spray paint. The nozzles were easier enough for little kids to manipulate, and they're easy to clean, safe, and spray like a straight up dream. Really, I can't recommend these enough. NICE PAINT. (Not cheap, but....write a grant or something.)

Kids combined button-pushing fine motor skills and large sweeping motions while experimenting hands-on with the materials street artists use on the regular. Lot of patience and turn taking and decision making too!
At the end of the day, we had two rad collab paintings to show:
"Ring Dash" and "Cool Kids"
So what other artists want to come in and do a demo? I want to host a million next year.