The Cutters. Someone with meticulous attention to detail and a steady hand should be assigned the job of "cutting in," or painting a straight edge where needed, such as along a wall where the ceiling does not get painted. Many products are available to assist, but none work as well as a person who's good at doing it freehand. Ensure this person is skilled (ask them to show you). A poor, jagged, wavy or splotched cutting-in job will jump out at you every time you walk by it. Why more than one cutter? This job is nerve-wracking and painful to hands and arms after a few days. You'll want to give this person a break after a few walls. House Painting
For walls, measure the linear feet of wall space (measuring along the baseboards) for the areas to be painted (using a tape measure, laser, or both). Then multiply this by the ceiling height (usually it is 7.5 or 8). If there are 2 story areas, measure them separately, and multiply them by double the regular wall height. Then multiply the total number by 2 (for 2 coats).
The BEHR PREMIUM PLUS 5 gal. Flat Interior The BEHR PREMIUM PLUS 5 gal. Flat Interior Ceiling Paint features a durable, splatter-resistant acrylic-latex formulation. It is designed for application on previously-painted or primed texture, popcorn and acoustic-style ceilings. The paint offers excellent coverage and resists mildew growth to help ensure that the finish remains attractive over time. More + Product Details Close House Painting
It's up to you. Outside is much harder because it requires more prep, patience, time, help, money and of course, effort. I have been painting my own houses and rental properties interiors for 20 years, and I painted the exterior of one, once. I then had it promptly done again by professionals who said it would have been cheaper if they didn't have to undo my work first. My advice is to get pros for the outside because everyone will see it.