First off, try calling the ford dealer and ask a service man about if it even needs turned in or if there is a trick to it. They usually don't mind answering questions.
Before turning it in just try using something softer than steel to push the pistons in, like a piece of wood. If that works, and you feel them bottom out, then you can try turning the piston adjustment in. Don't do that unless you can't get the new pads in first though.
Hope that helps.
Bo