I have read about the flush procedure in my 2003 Ford shop manual and the 5R110 trans fluid flush as ford expects it to be done requires a machine that they have at their dealerships. In your owners manual under the service interval listings for 35,000 miles (I just hit this mileage so it's fresh in my memory) the owner's manual says to drain the transmission pan and change the EXTERNAL fluid filter which on my truck was inside the right frame rail forward of the front axle and shaped like a small vertical can attached to the trans cooler lines. As the owner's manual describes it (and the shop manual confirms it) you will only drain out approximately 7.5 quarts. The trans holds 18 quarts so you don't even drain half of the fluid. Change the external filter, replace the pan drain plug, put 6 quarts down the dipstick tube, start the truck and let it come up to temp. Once up to temp, add the trans fluid in small increments (1/2 quart or smaller) until the fluid level comes up to the proper HOT operating range on the dipstick as described in the owner's manual under the Transmission Fluid - Checking and Adding section. Even though I only drained less than half the fluid, I know for a fact the transmission was shifting better than before the fluid change and it was shifting great to start with. Additionally, if I recall, the owner's manual doesn't call for a complete flush of the trans and torque converter until 60,000 miles. Hope this is helpful...
Obviously, if you feel more comfortable doing the full blown flush, by all means do so but I don't know of a way to thoroughly flush without the machine that is listed in the Shop Manual. By the way I used the Motorcraft Mercon SP and if I recall a full 18 quarts would have set me back approximately 75-100 dollars (can't remember exactly).
Well, if nothing else, at least I was able to give you some info...
Patrick
I couldn't help myself 
