Go down to the local tool rental place and get an airless sprayer. Airless sprayers work by compressing air and spraying it into the paint and turning it into a giant spray paint brush. The typical swath cut by the average airless sprayer is about 4 feet wide. Coverage is even and the control is awesome. Buy some killz primer and the paint of your choice. Get some visquene, masking tape, drop cloths, and a high volume output fan. A hat, overalls, and safety glasses would be nice too! Unless you plan on repainting the walls of the room(s), you will need to carefully mask them off. Same thing goes for all furniture, windows and floors. You can never cover things up too much. The reason that the ceiling is yellowing could be attributed to several factors such as cigarette smoke, age of material, etc... Unless you want the yellow to come through the new coat of paint, you need to prime the surface very well with killz or some other type of sealing, bad stuff killing primer. After the primer dries, you can paint the ceiling what ever the hell color you want to and the yellow will not come through the new paint. The advantage of the airless sprayer is the time you save applying the primer and paint along with the fact that it will not screw up the texture on your ceiling's surface. About 5 years ago my pops and I did our old house in about a day. It is about a 3800 sf house without the garage. That included set up, priming, painting, and clean up. This is the only way to go when you gotta paint a poop corned ceiling!