Search headland pattern on this forum.  There have been thread about this before.  I do all my fields using a headland pattern. I love it.  You can set how many circuits you want.  I.e. 2 with my 12 row planter, 3 with my 8 row head and one with the sprayer.  Also when I learned to pause the headland logging that made things easier.  

Just a quick tip.  You can pause headland logging.  When you do this it draws a straight line from the "pause" point to the "resume" point.  Kind of like an endless amount of seamless a-bs lines linked together. 

I start logging my headland, get to where I want my infill a-b, slow way down, set my A and then pause my headland logging, then drive to my B, slow way down and resume headland logging, then hit B right away.  This way your headland circuits will match your infill on the straight side.  I also do this with my tractor with no implement in the fall or winter.  I set the implement to 15 ft so my swath is just passed my dual on the tractor.  You can back into corners, get out and look down the line, adjust  as called for.  Then in the spring, hit the yellow steering wheel and you are golden.   If you pause  headland logging on the straight side you will probably have to steer the first pass if the side isn't perfect, but then all the  subsequent circuits will be aligned with the a-b infill.  Only autopilot will steer on the first circuit.  Pilot and steer with steer on the inner circuits.

Ask away if you have specifics.

I reread the op.  I've never shifted on the headland circuits so I have not help there.  I've never had trouble backing into corners or going around inside corners.  I know you can set or turn on and off the headland smoothing.  This might have something to do with your lack of success.   I make all kinds of funny squiggly lines at the inside and outside corners and after I complete the headland circuit the fmx or 750 smoothes the lines out an has a curve of some kind.  I usually can't use the line for guidance until i get on the 2 circuit of an inside corner as the smoothing isn't as perfect as reality.