Can someone describe the steps involved in this method ?
Pretty simple, actually.
Get a roll of 1/2" clear plastic tubing and a 5 gallon bucket from the likes of Home Depot.
Look at the bottom of the radiator - there are two 1/2" metal tubes going to either side of the radiator. Those are the transmission fluid tubes that pump fluid through the internal trans cooler.
Uncoil your plastic tubing, running one end into the 5 gallon bucket, taking care to clamp it or otherwise ensure it won't go flying out of the bucket when fluid is pumping through it. Take the other end under the truck near the bottom of the radiator, and put down a tarp or other means of protecting your workspace from inevitable fluid leakage.
On the passenger side tube at the radiator, slide the little black plastic cover back off the nut. There is an E clip that retains the flared tube in the female side - this can be a little weird until you do it once or twice, but it was easiest for me to push it back a little until I could grab it with needle nose pliers and pull it off. Grab your plastic tubing, and pull the metal tube straight back out of the hole. It will start to leak fluid - immediately push your plastic tubing as far as you can onto the end of it to run the fluid from that metal tube into your bucket. Stick a cloth or something into the open hole on the bottom of the radiator to prevent undue mess.
Start the truck - it will begin pumping around 5 quarts of fluid into your bucket. As soon as it starts to pump air instead of fluid, shut down the vehicle.
Now, drop the pan, replace the filter, clean the pan, and reinstall.
If it's not already on the ground, lower the vehicle. Pour 5 quarters of fluid into the dipstick, and let it settle. Prepare several quarts of ATF within easy grasp and with their lids off because you'll need to continually be pouring ATF into the dipstick as it's running.
Start the truck again - it will have quite a bit of air at first then will begin to pump fluid. Keep pouring in the ATF and watching the fluid pump out until it has the cherry red coloring of fresh ATF. Your bucket should be around 75-80% full at this point.
Turn off the truck.
Remove the plastic tubing, slide that E clip back onto the nut, and reinstall the metal pipe into the radiator. You should hear a click when it engages, and make sure it doesn't pull back out. Then slide the plastic cover back on there.
Finally, warm up the transmission and top of the fluid the needed.