Yep. That's the best way. Remove plug. Fill from top until it runs out of the plug. Put plug back in and get ATF all over your hands. Only way I do it.
Yep, its only done right if you get tranny fluid all over your hands. And its only done right if your blood, sweat and tears litterally go into your car My blood is all over my car, lol. I have cut myself numerous times, especially during the spark plug changes. lol. Amazingly enough, never during my tranny rebuild. And I am sure it will be plenty of times when I go to put some headers in the car.
Well you wouldnt get proper lubrication, The fluid would foam, and you would cause some nasty leaks. Which would be followed by you needing to take the tranny down to replace the seals. I dont think you want to do that
I open the fill plug and put a small baking pan (the disposable foil ones work good) under the tranny. When its full as long as its rweasonably quiet you will hear the fluid dripping into the pan. Stop pouring then of course.
Easy peazy Japanasy.