OK-- I went through the Atlantic British process which I knew may be wrong-- but things went strange fast. I got about two and a half quarts in the pan statically. Started up the truck and let heat up a bit then went through the gears and then kept it running. Went under the truck and started pumping in fluid- got about three more quarts in and it started to drip past the tube in the hole and I thought fine-- soon as I pulled the tube out to check how quick it was really dripping without the tube in the hole-- it pucked out two quarts of fluid. I am letting the truck cool down and will start over.
I think I proved that AB method of doing it warm is the wrong way to go-- all of the fluid in the tranny must have heated up - expanded- then blew out of the fill hole. Great that a supplier would make video which is wrong.
Now I have to go out and buy more fluid since it went back into my drain pan which was empty but still had dirt bits in it. I did pour it back into my empty bottles using a fine mesh paint strainer- but not worth taking a chance.
I measured the amount of fluid I dropped out when I first pulled the pan--about four quarts.
To some degree it would depend how much was in there to start with, you won't get it all out of the torque convertor, but when I've had to do anything which involved changing the fluid, I would reckon to have at least the full capacity available as your guaranteed to lose some somewhere along the process.
Your best bet is probabbly to refill it as best you can to the right level, drive it around a bit to let it get all the system filled up again, then recheck it as per the described method.
It would be much easier if it had the dipstick like the GEMS ones do.