Some painters, like I used to do, charge by the color, some charge by the job. I've seen some charge $400-500 for a simple job with light weathering, and I've seen some that will go $30 on basically the same job. But the guys that charge $400 are the true artists of the field, and their work is worth the premium.
There are currently several online here that do good work. One of the best would be Espeefan, (Alan).
Best bet for finding a painter is to:
1. See samples of their work.
2. Find out what time frame the painter can have yours finished in.
3. Get a set price BEFORE agreeing to have the work done.
4. Don't pay until satisfied. This was my policy. In almost 30 yrs of painting, I have had only one guy be dissatisfied. He got his loco back, stripped.