If you are just going to do drain and fill then I would just get the cheapest ATF you can find.
The $18 per gallon Valvoline Maxlife ATF from Wally World that JohnJMonroe mentioned is probably as good as any.
You dont want to buy really good synthetic and throw about 30% away everytime you drain and fill. Thats about $50 a gallon.
To even have a prayer of getting anything that resembles a decent ATF change you would have to drain and fill at least about 5 times, thats about 15 quarts.
I would go ahead and do it 5 times within a couple weeks.
Problem with doing this is that you do not drop the pan so cannot check your magnets.
Plus you are wasting about 5 quarts of ATF and taking A LOT more time and effort than just simply changing the ATF.
If you are not going to drop the pan then 90% of the work of doing a full ATF change is done.
All you need to do is drop the line from the radiator as shown in the link, put it in a preferably white bucket, start the car, let it run about 30 seconds which should be about 1 1/2 quarts pumped out, then pour in about 1 1/2 quarts and do this until fresh fluid is coming out.
"Kolelt
Notice the drain bolt on the transmission. That's like saying draining and refill engine oil is waist. Or you need to drop the engine oil pan everytime you change oil. There's a reason for the drain bolt in the tranny. And a full drain and refill is just fine. Personally I'd use Toyota automatic transmission fluid."
I am sure you must have misspoken or maybe testing out a new bong or something.
If you drained about 1 1/2 quarts of oil from your engine and did a "drain and fill" leaving the other 4 quarts in there then YES without any question that would be a waste of good engine oil.
The sole reason the Transmission drain plug is there is to drain the pan before you take it off (or to do a fairly worthless drain and fill)
When you drain your engine oil you are draining probably 95-98% of it.
When you drain your ATF you get at best 25-30% tops.