8 quarts is about what I get out with a simple draining. That makes it easy to get a 50/50 mix by simply adding a gallon of antifreeze and a gallon of water.

To get as much as possible out of the system I use the block drain and then loosen the lower radiator hose at the waterpump. There is no way around some spillage but with the lower hose still connected to the radiator you have some control over directing the flow as you lower the hose.

Several buckets of water to flush the area of any spill will dilute any reasonable spillage enough not to be a danger to peoples pets licking up undiluted coolant.

Now that the weather is moderate (at least in my part of the world) I would simple fill the system with water and drive the car. Remember to move the heater control to heat to flush the core. At the end of the day drain the system via the block drain. Refill the system and drive for a day and once again drain the system.

A gallon of G-05 and a gallon of water should get you close to a 50/50 mix of coolant in the system.

Randy