Cold hands, teach the old European chefs, make poor bread and fine pastry. The reason is that bread loves warmth, but pastry works only when everything is well chilled and lightly handled by cold fingertips. Flaky crusts are achieved when the flour and fat and water in the pastry is mixed only enough to hold it together so it will roll out. Overworking the dough results in tough pastry.
Do not touch the pastry with your fingers at all while you work the fat into the flour -- just cut through the fat with the pastry blender or two blunt knives until the mixture resembles bread crumbs.
The water (or egg and water) must be thoroughly chilled, and added by degrees to the pastry using one blunt knife. Once the water is added, the gluten in the flour has a chance to start developing (desirable for bread but not for pastry). Add enough water to form moist clumps, but not enough to form a ball of pastry. You can always work more water into the dough, but a wet dough is difficult to remedy.
Turn the clumps out onto a lightly floured board and continue cutting in with the knife -- this draws the moisture out of the dough -- and the dough will suddenly be moist enough to come together in a ball. If it doesn't, sprinkle the dough with a few drops of water and continue cutting them in.
Now scrape the dough off the board, dust the board lightly with flour, and gently bend the outside edges of the dough into the center all around -- this is a form of kneading -- until the dough has one smooth side, with all the seams tucked underneath. Flatten the dough to a cake, then chill as directed.
Roll the dough gently, turning the pastry often to prevent it from sticking to the floured board. You should have a flaky crust.