Welcome to CAD Morraco!!
I like to grease my fifth by pulling out until my plate clears the trailer. (you are lined up nice...cuz you just unhooked). I'll dump my air and back in about the two foot or so to get most of the plate back under...(and I always get out and look-see).
When you do this a lot...you get a good feel for it. I pick a spot on the ground and back slowly. Then I air up and finish the hook.
A good greased fifth helps you manuver well in moments like backing.
Like someone mentioned...you risk backing the kingpin past the fifth...if you are not careful. I've done that a couple times.
Also...grease less...and grease more often. It gets easy to do...and less messy when you figure it out.