Eric, what you want is small crown molding since you are talking about installing it at the junction between your wall and ceiling. The difference is that the cove molding starts off as a square and the cove is routed in it. Crown molding looks similar from the face side but is actually a lot thinner so it can follow the inevitable bumps and waves in your walls and ceiling. You will have to find a shape small enough not to go beyond the gridwork for your ceiling. The place for instructions on how to cut it is www2.fwi.com/~fruny/ . Yes, you will need a miter box but since you will be working with a small shape, a hand powered one will be fine. Perhaps you can find a really one to rent. You will need a coping saw also but these are pretty cheap.