You'll need heater set to hot before you do any draining.
Usually 2 bleed screws, one on the top left of the rad, as you look at the car, and one just before or after the heater marix, likely to be after i think.
The few times i've drained cooling systems, i've generally found that the quoted amount that the system takes never comes out.
Another good idea is to use radflush type products about a week before you do the change, make sure the car gets fully up to temp at times to alow the mixture to flow through the whole system