Our recent Nature Art Class had alot of fun making natural paint brushes out of yucca plant stalks and horse tails and painting with Earth Paints. The Southwest Native Americans had yucca plants all around them (but they grow in many other places - like my backyard in Oregon) and used them for painting pottery and fabric. Other plants to try are mullein, iris and cattail stems.
How to Make Native American Paint Brushes:
Yucca Plant: Chew on the end of the stalk for a minute and then use your fingernail or a knife to scrape the green plant material off of the fibers into a brush-like end. Very Simple. You can even use just one fiber for very detailed work.
Horse Tail: These plants grow in lots of gardens wild and are a ready made paint brush.
My 2 year old painted his wooden trucks with horse-tails and Earth Paint.
Isaac painted this beautiful portrait with only his yucca brush and earth paint
Django paints with horsetails from the garden
Yucca stalk art