Contractors apply several layers of paint to achieve a suitable finish. They leave the first coat to dry for the recommended time and apply one or more finishing coats. They might choose paints with special qualities for different types of room. Manufacturers have developed paints for bathrooms or kitchens that have good resistance to moisture for example. When they have completed painting, they clear away any equipment and restore the area to its original condition.
My wife and I just painted the interior of our house with about 6-8 gallons, of $30+ per gallon (meaning the good stuff, non-diluted) with absolutely fantastic results. However we just paid an average of $5 per gallon. Reason...all big box stores have paint, set aside, that has been mixed but not picked up by the customer. They need to sell it quick and if you're not in a hurry (you know well in advance that a room or two need painting and it's not like the roof leaking and needs an immediate fix) you can go to each store when you need other supplies or food, like Walmart (when convenient, driving 20 miles to each is not worth it) and over the course of a month or two, pick out some very nice colors of quality paint. We found perfect colors...not saying they were our first choice but when we opened the can, very nice and some even better than our original picks. Cost to paint the entire house was about $100, with all materials included, period. We had it on the market for a few months to sell, didn't sell, painted the rooms, got 2 offers the day after we finished, took the best one and never looked back.
To win work, contractors generally have to bid against other suppliers. To make an accurate bid, they estimate the time and materials required to complete the job. They measure the area to be painted and discuss the type of finish the customer requires. They assess the quality of the surfaces to work out how much remedial work they must carry out before painting. They might have to remove old paint or wall coverings, or repair cracks and other damage. They also calculate the cost of any essential equipment, such as scaffolding for exterior walls.