The best way to do it is to take out the radiator, take out the thermostat, put a hose in the block where the top hose was and flush with water for a few minutes (or until the water comes out clean). If you can get the drain plug out of the block (on the turbo side) then it will help get some crap out as well, but most of the time its to tight to pull out in the car.
Flush the radiator and put it back in, you can flush it in the car, but you may as well pull it out of the car and clean the fins out a bit as well.
Bleeding - Fill the radiator with coolant until it stays at the top, this makes sure most of the block etc is full of water, start the car with the cap still open and get the car hot, continue to fill with coolant if the level goes down. When it doesnt seem like any more is going in then you can loosen the bleed screw and keep bleeding from there till no more air comes out while making sure the level in the radiator is still good