We have one of those machines in our small truck shop that pushes new transmission fluid through while it flushes out the old.It takes a few extra quarts to do this.It’s suppose to clean out the filter so you don’t have to remove the pan to replace it.If you do the drain and drop the pan to change the filter method,you’ll have old fluid trapped in the torque converter.That’s why the flush method is recommended so much.
I had this done by my independent mechanic to my 1996 Lincoln TC tranny. At about 75,000 miles it had developed a "stuck" shift - shifting with a clunk. I was reluctant to take it to a transmission specialist without at least trying the spin flush. After the flush, we added some super lube for transmissions (can't remember the name).
Lo and behold, the clunk disappeared and at 115,000 miles the tranny still shifts like a new one.