Similar to Blazblue, you must train for 30 minutes straight while actively moving your character in some way shape or form. While in practice mode, I pushed Labrys back against the edge of the stage and simply mashed b for 30 minutes and the achievement popped with no problem. Some people report turboing it doesn't work with certain moves, though it did later on with a similar move. All I can confirm is using the same move with Labrys for 30 minutes worked for me.
Simply leaving it in practice mode will NOT unlock the achievement.