Trailer Hitching Issue

I just bought a new 2720 TM. I had no problem towing with my Nissan Titan. However, after I backed the TM into my driveway I could not get it un-hitched. The problem is my driveway is on an incline, therefore there was too much pressure on the ball hitch. I chocked the wheels and tried moving the truck back and forth to releive the pressure, but still could not release the locking mechanisim. I eventually just pulled the pin at the receiver at the truck and lift and pulled away leaving the ball hitched. Any suggestions on hitching and un-hitching on an inclined (not too steep) driveway.

Thanks

Dan