If the point of hiring a well established, experienced, reputable painting contractor is to secure the professionalism and trust suggested to be inherent with that choice, then I would EXPECT that professionalism and experience to include the ability to make the proper and correct calculations for labor and materials for a fixed price quote, and there should be NO reason for the contractor to put the cost burden of their miscalculation on the consumer.
To maintain a wet edge, start near a corner and run the roller up and down the full height of the wall, moving over slightly with each stroke. Move backward where necessary to even out thick spots or runs. Don’t let the roller become nearly dry; reload it often so that it’s always at least half loaded. Keep the open side of the roller frame facing the area that’s already painted. That puts less pressure on the open side of the roller, so you’re less likely to leave paint ridges when doing DIY wall painting.

Sorry it is difficult to trust almost anyone in the trades. It is easier to do the work myself and not deal with strangers in and around my house. When I have to hire someone I tell them up front that I'll be checking every detail, pay extra to purchase the materials myself, and if they don't want the job - well good! I always fine someone who will work with me as I pay a bonus for that.
You can save a bundle by doing the labor yourself. The biggest DIY expense is paint. Other expenses include buying or renting supplies and equipment, like caulk, primer, brushes, rollers, tarps and ladders or scaffolding. Freeman advises applying paint with brushes, not a sprayer. “If you overspray all the window frames and overspray your shingles and your sidewalks and the brick on the front of the house, you do damage that is not easily fixed,” he says.

Ryan, David  and Erin were so  helpful during the entire process. The team was easy to work with, detail oriented and efficient. Because of this the entire project went smoothly, from the in person consultation, scheduling and throughout painting process. Hector and his crew did a wonderful job. They came in on time, asked questions when they needed to, polite, hardworking and most importantly excellent at their jobs.
In general, glossier paints are more stain-resistant and scrubbable. But a higher sheen also highlights any imperfections in the wall or in the paint job. "Flat paints are fine for ceilings and formal rooms, but for most of my customers, I recommend an eggshell gloss. It's good for hallways, kids' rooms, even kitchens and baths," says Toto. It seems that latex paints have won over even the most finicky painters. "Though we still use oil-based paints for restor-ation work, latex paints are fine for interior walls and new trim," says Toto, "as long as you don't go cheap on the paint." All of our pros have their personal favorites, but they agree that good paint does not come cheap. "You'll spend $20 to $35 per gallon for a top-shelf paint," says Weeks. The pros also agreed that using two coats of paint will result in the best-looking job. Don't skimp on the coverage; if you're covering more than 400 square feet per gallon, you're spreading it too thin. Also, keep 1/4 to 1/2 gallon on hand for touch-ups.
The perfect roller would hold a roomful of paint, leave the right amount of texture, wouldn't spray or fuzz, and would be easy to clean. Until somebody invents the ideal one, follow these tips to choose the right roller. "The longer the nap, the more paint the roller will hold, but it will also create more texture." says Dixon. "A 1/2-inch nap lamb's-wool roller holds plenty of paint without too much texture," says Dixon. "Less expensive rollers can work," says Span. "Just wash them first in dishwashing liquid to remove any stray fibers." Most of the pros we spoke with prefer 9-inch rollers over 18-inch models -- they are lighter, cheaper, and easier to use. Despite these shortcomings, Maceyunas swears by the wider roller. "The roller can do a whole wall in a few up and down strokes instead of in several dozen W and M strokes," he says.

House Painter Co