I offered this on a similar post. It's all manually, no automation. I also added that on a 10 mile map playing "hunt them down" you sometimes may have 30 minutes before the enemy is sighted, which will be a road.....Protect the roads where you are advancing first....and then organize the remaining troops.
Anyway....
I play mostly Sandbox, that is I play against the AI. I guess there could be a realism argument between playing Courier or not, but I micro manage, which if you feel you enjoy the game this way, you might find this helpful.
In Sandbox, it's a must to micro manage down to Brigade Commander or you will have Regiments that will advance or wander off towards the enemy, and in most cases, you'll see high loses with no gain. I normally begin the battle and advance under Corp Commander Control. If I find ground that I like or know the enemy is approaching (they approach by roads) I then Control down to Division Level. Hopefully having enough time, I then control down to Regiment Level, but leaving my artillery still under Division Level Control. Once the battle lines are drawn, I then control my artillery individually as they can wander off at times.
There may be better ways to control or play the game under Sandbox, but this way makes me happy. I don't think the AI is sending couriers on every move they make...
the reb