The easiest way to flush:
1) pull the pan by tapping the front corner with a flat screwdriver...bolts loose...clean the pan well...install new filter....clean the magnet and put it in place...reinstall the pan making sure there is no lint or RTV in the pan or around the flange....do not overtighten the small bolts.
* I used filter kit with a rubber gasket that can be reused...AdvanceAP.
2) Add approx 3 qts ATF to the trans...remove the BOTTOM hose at the radiator*...put the end of it in a bucket...run the car at idle for just long enough that the flow almost stops. During this time you can shift thru the gears.
* earlier Focus had regular hose clamps?...later ones various types of special couplers...good luck with these.
3) Add another 3 qts ATF slowly and THEN do the SAME AS ABOVE.
4) Replace the hose at the radiator....securely.
5) Add another 3 qts ATF slowly to avoid hiccups
....ATF coming back out of the tube.
6) Start the car up and look around under there for any leaks...clean drips off with a rag to check for sure.
7) Take the car out for a drive...10-15 miles...find a level spot of ground and check the fluid level when HOT....level should be between the top and bottom lines.
note....trans might act a little strange till it adjusts to the new fluid...make sure you end up with the correct level.
Recheck for leaks.
For the most effective flush...you would use regular Mercon V fluid (6 qts) the first time...drive it for 2-3-4K miles...then flush again...this time leaving the pan and filter alone
...just running 3 qts out through the line...adding 3 qts synth ATF...run 3 more qts out...add another 3 qts synth...replace the line. Check the level and add right amount of
Lubegard ATF additve.