Some contractors work on time and material others on a firm contract. I would never hire the former and am leary of the latter. A contractor may low-ball a bid to get the job planning to make a killing on change orders. If you say good morning to them, they charge you extra for that. If the contract is not very, very specific and extensively fleshed out or if they display their change order schedule prominently on top, show them the door.
With that said, here's the reality of that particular scenario. Painters do put water in the paint, but not for reasons you would think. Some materials need to have their viscosity manipulated in order to slow drying time, allowing gravity to 'smooth' out the product for a better finish. It also prevents 'drags' and 'sausages'. I personally try not to do it too often, but from time to time I have to. I want my client to have a proper finish.
Interesting information! We just got scammed in White Stone, Virginia... we chose the same color, but went from a flat to an eggshell finish. I wasn't available to stand over the painter while he painted. For such a detailed job, I marveled at how quickly he finished the project! After he was paid for the job, we discovered all he did was roll paint across the walls and close to the crown, baseboards and detailed trim around windows and doors leaving about an inch or so of the flat finish. By using the same color, he didn't even do the job he was paid to do, which explained why he could finish the job so quickly. By using the same color... he got lucky and passed it off as a completed job not bothering to paint to and cut in around the trim. Upon further evaluation of our walls we could see exactly where he stopped because we could see the difference between the flat and eggshell finishes. There are walls he didn't even bother to paint. Then where he did paint near the crown when we were in the room watching ... he hit the crown moulding and tried to tell us it was already there... and tried to sell us on painting the crown moulding. I am so disgusted and upset!! He'll be hearing from us to rectify the situation.
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.
O'Neil patches shallow holes and divots with Ready Patch because it dries fast, sands smooth, and stays flexible. Deep cracks and rotten spots are best repaired with two-step epoxies, such as those made by Advanced Repair Technology. (For a step-by-step instructions, see Repairing Rot with Epoxy.) The days of using polyester auto-body fillers on wood are over. "They cure too hard," says Portland, Oregon–based painting contractor Kathleen George. "They look good at first, but then they peel away."