If you're going to do any part of the painting or prep work on your own, you must know that the first step in preparing a surface is washing it. Since dirt can affect the smoothness of a surface area -- and therefore paint's adhesion to it -- use soap to remove any dirt or stains. Make sure there's no soap left on the walls when you're finished; also make sure to remove any gloss with sandpaper and vacuum up the leftover dust.
Only a dummy gets involved with so-called "contractors." Hire a qualified actual worker yourself. Check out their resume/background, etc. RULE #1..NO ADVANCE DEPOSITS! Pay daily or weekly or upon satisfied completion according your standard, not workers. Contractors are merely employment agents. If that's the way you get work done, then go ahead and waste your money and wind up with the myriad of problems enumerated upon in the news clip above. RULE#2.. NO SMOKERS. They are lighting up on your money. RULE#3: No cell phones while working. Talk on their own time after work
I do not mean to come off with an edge, however, this is an article for people hiring low bid, uninsured, one man band painters out to "hustle" a buck. Hire reputable, established companies or hire someone you know or have a strong referral from. If you are arguing over watered down paint, ticky, tacky deposits, buying your own supplies, you have hired the wrong guy.
Some proposals simply say to paint the walls and ceiling and never specify the number of coats to be applied. If the colors are similar enough, it's possible to get away with one coat of paint and not discount your pricing. No matter how hard you try, tiny, pin-sized air holes will pop exposing the original walls. This may not bother you if you can't notice it, but principally speaking you should have paid your painter less for the work.
Recently I had the outside of my home painted. The contractor wrote a good contract, but I failed to realize that some things were not in it. It reminds me of the car dealer who offered a good price on a new car but failed to mention that it did not include tires. My contractor failed to specify that lattice under a porch was included. So the painters did not paint it. To his credit, he did instruct them to paint it when I brought it to his attention. If I had the job to do over again I would look for an individual who came with referrals from happy customers rather than a franchise owner..