For bigger houses or for faster work on smaller ones, rent a high-pressure spray cleaner. This device attaches to your home's water-supply system and puts out a jet of water at a pressure of about 600 pounds per square inch. It is equipped with a handheld wand tipped with a trigger-activated nozzle. The pressure is high enough to dislodge not only stubborn dirt, mildew, stains, and dried-on sea-spray salt, it's enough to remove peeling paint. In fact, if the jet nozzle is held too close to the surface it can even peel off perfectly sound paint, split open shingles, and drill a hole in siding. So follow the manufacturer's directions and wear goggles and protective clothing.
Here is where this affects you as a consumer. You select a painter with a contract that says 2 coats, $500 down. You give the company the deposit and pick your colors a couple of days before the project starts. The painter goes to the store with your colors and figures out they are deep base. He (or she) not only needs to charge you more for the paint, but he also needs to charge you for a dark gray primer coat. Ninety nine percent of the time that primer coat is going to be really, really expensive since you already gave a deposit.