Put a 1/2 bowl of milk in the sink and fill a similar bowl with water and pour it into the bowl of milk. Repeat filling the bowl with water and pouring it into the bowl of milk until the milk bowl has clear water in it. How many bowls of water were required to get the milk totally displaced?
And put a vertical doughnut full of milk connected to the bowl only by a small opening on the inner edge with a shaft running into it.
I would be willing to wager the cost of a flush job based on the condition of the pan when it is dropped. After a “by the book” total flush if the pan is pulled and there is no black scum or a coat of balck iron dust in the pan I would pay for the job. I’d wager double the price against the price of a good steak dinner.
Is there consensus then that a transmission fluid exchange machine will do a good job of replacing the transmission fluid provided the pan is dropped and all the pan fluid drained first? And the pan cleaned, and the filter replaced. And if those steps are not done, just the fluid exchange machine hooked up as is, then the result is not such a good job?