Painting on Rocks
To paint on rocks,you will need smooth stones from rock garden or landscaping purposes. You first need to scrub the rock with a brush & comet cleanser & water to clean the rock.
Rinse well and let dry. Holes or other small flaws that can't be worked into the design can be camouflaged by filling them in with a bit of 3 in One brand Plastic wood, a product that dries quickly and can be painted over.
I have also used plastic wood to stabilize the base of a "tippy" rock. To make chimmeys & to add dimension around windows, doors columns, etc. Use the wood putty and let dry.
Then paint the rock with acrylic paints, let dry thoroughly before sealing. To seal: use spray-on polyurethane or wipe on an acrylic finish such as Future floor polish with a lint-free cloth.