On those days where your kids want to paint and yoyu don't want a mess to clean up. Make this simple paint that can be washed away by water. If your child is a sensory avoider rather than use a brush they can use a spray bottle (the spray bottle can also be used to paint the snow).
This paint washes off easily. It is biodegradable. It won't harm your plants because it's eco-friendly. This can also be stored if you have any left. If they should dry up just add water. How easy is that?
1/4 cup cornstarch
1/4 cup water
Mix the water and cornstarch until smooth. Add the food color and send the kids outside to the driveway or sidewalk with brushes. If you are using spray bottles fill them up and send them outside.