Here's a way to cut bar cookies:
Fit a piece of aluminum foil into the pan so that it extends a few inches past any two opposite sides. Trim the other two sides to fit. Prepare the foiled pan as directed in the recipe. After baking, remove the pan from the oven and run a small spatula or knife to separate the dough from the two sides without foil.Cool the pan on a rack. When cool, place in refrigerator for a few minutes, then use the extended foil to remove the baked dough from the pan. Invert to strip off the foil. Invert again, and cut.
Also, the best way to cut brownies is to use a disposable plastic knife. No rinsing under hot water necessary. -- Melissa Clark