Using an airless sprayer to place paint on the wall (using low pressure) will speed up the process because your not having to dip your brush or roller. spray about 3 or 4 sq. ft. and then back brush or roll spreading and evening the paint. Because your using low pressure, mask and cover is at a minimum once you are accustomed to handling the spray gun and the type of surface being painted. Overspray will be larger droplets they tend to fall, than float around.
In my opinion the information on this page should be modified as for the pricing for my area is not correct and the information here could damage the expectations of my or another painting companies pricing. There are too many situations that there is not a way to specify cost prior to seeing the actual house and that information needs to be in big print on this page. http://youtube.com/watch?v=b6_WEt9k_Hw