While cooler water holds more air, you'll need Oxygen to fill the bags. Fill the shipping bags enough so the Koi "Floats" in the water, this is normally where the water is just above the eyes. I push down on the Koi once they are in the bag, if it's belly is still touching the bottom, add more water.
Use what most call a Pan Net, only guide the Koi with the net, NEVER lift a Koi of that size out of the water with a net. Have water in the Bag and slide the Koi into the bag as it's resting in the net at the surface. Lift the Koi out (Holding both ends of the bag so it remains long, not on it's end.
Unless you have Koi Shipping Boxes, use large coolers. Make sure the bags & coolers are longer than the Koi. If not the Fins will get ripped. When placing the Box/Cooler in a car, always have the box/cooler pointing to the side of the car, not toward the front/rear. If you must break quickly you won't damage the Nose or long fins of the Koi.
Any more questions, I'll try to follow the thread. Good Luck