Rocks
Rocks are like fingerprints–no two are exactly alike–which makes them
 a great art base. Patty Donathan, a prolific rock painter, claims the 
most ideal rocks have been weathered well and tumbled and rounded by a 
water source like a river, creek, lake or ocean. Look for rocks on 
beaches, dry lake or river beds. However, always be aware of your 
surroundings. Taking rocks and stones from state and national parks is 
forbidden. Don’t let this be a deterrent to rock painting as a whole. 
Rocks are everywhere, and looking for them is half the fun. If the rocks
 are dirty, clean them with warm soapy water. Scrub them lightly with an
 old toothbrush, rinse them in cool water and pat them dry with an old 
towel.
Brushes
Paint with inexpensive brushes. Depending upon the hardness or 
softness of the rock, the surface will wear down a brush quickly, making
 expensive brushes a waste. Look for brushes that are durable and have 
long bristles that hold a lot of paint. Consider buying a stiff brush 
with a wood handle. They are generally inexpensive and work well when 
painting on rock.
Selecting paint
Acrylic paints have improved through the years, and finding quality 
paint is not as difficult as it was in years past. According to Lin 
Wellford, a professional rock painter, if the plan is to showcase your 
art outdoors, use an acrylic patio paint. Patio paints are formulated 
specifically to weather well in the elements and are designed for porous
 surfaces like rock, clay pots and stepping stones. If you plan to 
display your art inside, any acrylic paint will work. The consistency of
 the paint should be neither too thick nor too thin. Add small amounts 
of water to thick paint until it reaches a good painting consistency. 
Practice painting thin lines on scrap paper or newspaper to check your 
paint’s texture and thickness.
Sealer
There are a multitude of sealers to choose from. Choosing the most 
effective acrylic sealer will ensure the art piece lasts a lifetime. The
 use of an acrylic spray gloss enriches colors and provides satisfactory
 protection if kept indoors. Choose a spar urethane sealer if the 
finished rock painting will be displayed outdoors. Although spar 
urethane is used primarily for wood, it also works well as an outdoor 
paint protector for rock paintings. Spar resists cracking, peeling and 
yellowing and protects against water, sun damage and salt air.