[villagetinker]

You could possibly save yourself some money. Painters tape is the way to go. Paint the wall the one (main color), let dry, apply painters tape to the areas you want to stay that color. Now this is important, use a 'dry' brush (very little paint) and dry brush the edges of the painters tape, and let dry for a couple of minutes, then go ahead and finish with normal paint. Allow to dry, and then repeat the process if there are additional colors and strips.
This method works great along molding etc. and smooth surfaces, if you have the typical orange peel walls, you will need to make sure the painters tape is in direct contact with the entire wall surface (press hard when applying), any gaps and the paint will wick underneath.
Hope this helps.