I'm new here, but have done a few transmission "flushes" and "drains and fills."
Re: Flushing.
Nothing gets "stirred-up" when you flush a transmission. It can be done with a machine or a bucket and a friend. The flush is done at the connections to the transmission oil cooler next to the radiator. I used to do it on my Mitsubishi Montero (Aisin Tranny). All I did was disconnect the tranny cooler supply line and direct the fluid into a bucket. Start the car and then as the fluid starts draining out you pour fresh fluid through a funnel through the dipstick tube. It is not as hard as you would thind to keep track of the amounts. Initally the fluid will be dark, then all of the sudden the fluid goes clean and then you stop. Reconnect the hose then top up the level. Doing this method replaces almost all the fluid with fresh fluid. I do agree though, if your tranny fluid has not been changed for 100k miles i would not do this method.
Re: Drain and fill.
For this method you just open the drain plug and you get maybe 3-4 quarts out. Then replace that through the fill tube. For this method you are only changing about 30% of the fluid at a time, so you would want to do it more often.
Most dealers flush the fluid so that they can get a complete fluid change. They use a machine like in the youtube video, although there are a variety of diferent types of machines. I have seen one type that is like a big piston in a tube. The piston separates the clean from the dirty and the piston also measures in the same amount of fluid in that you take out.
I plan on doing a diy flush on mine soon. Ill post the results.
Re: Trannys with no dipstick.
I recently changed the fluid on My Audi A4 which has a tranny like this. First you drop the pan and change the filter. Then, tt is a bit harrowing of an experience for the home mechanic since you need to raise the car up while keeping it level. They go through a few procedures to get the old fluid out, then refill the fluid through the drain hole with the car running while monitoring the fluid temp with a computer interface. While this method gives you a fresh filter, it does not replace all the fluid.
BTW this Mazda tranny has a filter that can be changed by dropping the pan, it is just that the dealer hate to do that.