Spray painting is usually used when large area needs to be painted the same color, or on rough exterior surfaces where pressure is necessary to achieve good results.
Most of the painting contractors use airless sprayer. It is called airless because it doesn't use compressed air. Instead the paint is forced though the small hole in the painting tip by the pump, producing the same result as conventional sprayer. The overspray is a drawback of an airless sprayer, because it usually means considerable loss of paint and a lot of masking prior to spray painting.
Here are some of the basics of spray painting.
The gun is held about 12 inches away from the surface. If the surface is smooth it is spray painted at the straight angle, if it is rough it may need to be sprayed at different angles to cover previous color. The paint overlapped 50 percent in order not to leave any lines.
If the surface after spray painting is not uniform and you can see paint lines, there may be a few reasons for that:
A spraying tip is too old and worn out, and needs to be replaced.
The pressure is not adjusted well, and pressure settings needs to be changed.
The paint filters are clogged up and need to be cleaned or replaced.
The spraying tip is too large and the pump can't produce enough pressure to support the tip.
Using reversible tip can help, if the the tip clogs up often when the paint is not strained well. Painting extension with adjustable end, can save a lot of time by not having to climb up and down the ladder when painting a two story house.
Spray painting is the easiest part as it can be learned very fast. It is the preparation work that requires a lot of experience. One can learn how to spray paint after painting 3-4 houses. However if your own house is your first painting project you are trying to undertake, better not to try to do it yourself, but to call professional painters, that already made all the mistakes on someone else's house and have the experience to provide you with a quality work.