I am not sure you need to make a battle plan to get the planing bonus.
From my simple knowledge planing bonus increase as long as your division is idle at the controlled borders of an foreign nonallied country and decrease if the division
Basically planing bonus is basically a second organization value for divisions on the offence and can be compared to entrencement for defensive divisions.
- Not at the borders of an foreign nonallied country.
- Are moving
- Are fighting