How do you get your heroes to hold 90,000 troops each?

Orange heroes have 2 skills that affect the amount of troops they can lead. The first skill that is always unlocked called 'Dictator' will increase the number and then the 6th skill called 'Awaken' will give other buffs and also a percentage increase to the dictator skill.

On top of this the level of the relevant barracks building for the APC will also affect the number of troops in each formation. If you have a level 25 barracks with orange heroes with both skill maxed out then you will be able to have over 100,000 troops in each line.