I've talked with a indie shop in the DC area and their version of a "flush" was to drain the fluid in the veicel > fill it up again > then run the vehicle for a bit [ ? 30 -50 miles] then drain that fluid and then fill up the tranny fluid once more > they chnage the filter ..

I would think any process that does not change the filter is flawed...

Personally > I did the job myself > drain pan and torque converter and chnge filter..