Any painting contractors you consider should be fully licensed, bonded, and be able to demonstrate good workmanship. These are the bare minimum requirements that you need so do not settle for anything less or you put your remodeling project at risk.
Painting contractors are licensed in most cases through the local city or county. They should also be able to show you verification that they are bonded and insured. This is for your protection as well as theirs, so that if something is damaged or someone is injured while on the job there is sufficient coverage to make repairs and take care of the injuries incurred.
You will find that different painting contractors tend to work with different brands of paint and different paint supply stores. Often this is because they can get a preferred contractor's rate at a specific supplier or because they feel a particular brand is of better quality than another is. Most contractors will allow you to select the brand of paint and the supplier but that may come at additional cost. Some contractors also offer a certain level of guarantee on their work and if you choose paint or a supplier other than what they usually use it may negate whatever guarantee is in place.
Evaluate all painting contractors carefully, including checks with the Better Business Bureau and thorough checks of references. Inspect the quality of work at some of their previous job sites, and talk with their other clients to get a sense of what to expect if you hire that particular contractor. If you pay attention and do your homework, you will be much more likely to find a painting contractor that meets your needs.