kp, my feeling is that you are better served using the same joints as you do for crown molding--45 degree beveled cuts for outside corners and coped joints for inside corners. A coping saw is not a big deal since they only cost about $6. If you plan to paint your chair rail, you can use paintable caulk. If you plan to stain, don't use the caulk. You might even think about prefinishing the molding if you plan to stain and you might want to have an extra prefinished piece or 2 for a "just in case" situation.