After replacing the radiator and flushing the cooling system:
Supplies:
5 Gallon bucket
rubber hose
4-5 gallons of Mercon
long neck funnel.
Raise LF of vehicle and remove LF tire.
Disconnect cooler return line from transmission. Locate at the 2 o'clock position as facing the end of the transmission directly above the TSS sensor.
Connect rubber hose to metal hard line, put other end into bucket.
Remove dipstick, install funnel.
Start engine. Fluid will pump out.
Pour fresh fluid in while watching the fluid coming out. When the fluid coming out looks fresh, stop adding but leave the engine on until the fluid flow starts to sputter. Turn off engine.
Reconnect cooler line to transmission. Reinstall wheel and lower vehicle.
Add 2-3 quarts of fluid, then check level of fluid with dipstick. Add fluid as needed to get to proper level.
Drive vehicle until transmission fluid is at operating temp. Recheck level, add more if needed.
Dispose of old fluid properly.
Monitor fluid level and quality carefully.
This will replace almost all of the fluid (about 90%) in the system.
In your case, I'd repeat this after about 1000 miles.
I use this same procedure on all my Fords. It closely mimics the T-Tech service, except it's fully manual instead of an automatic process.
Steve