Paint the base coat on the walls first. Basic painting is the foundation of faux finishing. A good base is important. Learn how to effectively cover the walls in plain paint first, including cutting in the edges and using a roller by watching a video and then trying it yourself on a piece of foamcore. Practice painting on several pieces of foamcore as you will need them later for practicing faux finishing.
Make the glaze in a paint tray or empty paint can, making sure it is well-mixed. To do a faux finish of any kind, you need what is known as glaze. There are two ingredients in a glaze, one part paint to four parts extender liquid. The extender liquid slows the drying time of the paint to allow it to be manipulated.
Learn broken color wallglazing techniques, such as ragging and sponging first, as they are the easiest and are often the first step in more complicated finishes. Take one of your painted foamcore boards and cover it with glaze. Use a clean, bunched up rag to remove the glaze from the board. This is called "ragging off". Use a hog hair or badger hair brush to soften the effect. Watch videos and read books that explain the variations of broken color techniques, such as colorwashing and frottage. Experiment with different colors of paint and glaze, noting the different appearance of each combination.
Learn techniques that are more complicated such as marbling that are based on broken color. Marbling begins with ragging off, then layering colors on top, using a badger hair softening brush to create indistinct lines. Faux lapis lazuli is also based on broken color. Use foamcore boards to practice and experiment before trying any of these techniques on a wall.