Complete instructions as well as more examples can be found on my website. http://www.gardensandcrafts.com/bbart.html
Step 1: Finding and Preparing your Bowling Ball
Always start with a clean and prepped bowling ball. Use rubbing alcohol or vinegar to get the wax finish off the ball. Sand lightly to rough up the surface, then rinse and dry the ball before painting or gluing.
Step 2: Painting your Bowling Ball
Use a paint designed for plastics, or use a plastic primer before painting. I find that spray paint is easier to work with. Always choose a paint that is rated for outdoor use.
Sealing a project with 2-3 layers of an outdoor polyurethane will help the paint job last longer. This ball is painted with a copper colored paint and has been in my garden for four years now.