I wish it were that easy to recommend that. It really just depends.
Not that it really matters, but why is the Militia playing as insurgents?
Mission balancing is tough. What I like to do is, I slow the game down. I use 25-50% for virtual AI speed. I also like to limit the friendly objectives a step or so higher in filtering than the enemy side, so players won't get interfered with too too often when patrolling.
The way insurgencies work is, depending on your starting settings, it can take awhile for the insurgents to establish themselves and build their HQ's. Upwards of 2+ hours if you've set everything conservatively and to the slowest settings.
Remember, Insurgents can only replenish their forces from the civilian population. So they NEED these civ recruitment HQ's to maintain and grow their strength.
What I like to do is setup a mission the way it seems ok, then use the profile counter and fast-forward and I watch for 2-3 in-game hours to make sure the insurgents aren't getting wiped down to nothing.
Then, as they finally establish their recruitment HQ's, I watch again to make sure they don't then grow too fast (remember, for all intents and purposes, there is no "cap" on how many soldiers the insurgents can recruit).
Meaning even if they seem like they are getting beaten pretty badly, they CAN (not always) grow so big you'd never be able to defeat them.
Generally what I like to do is have the starting forces be at least equal, or generally, have my side out number the insurgents by a little bit. And I have my side filtered just a bit higher than the insurgents in the objective modules.
At first the insurgents will take losses, but eventually, they'll catch back up. If after 3-4 hours, the numbers seem ok on both sides, I figure that's a good enough place to start.
There are lots of ways to balance missions to get the results you want. These suggestions are just one way of lots and lots. One popular method amongst the community is to only give insurgents civ obj's and only give friendlies mil obj's. That way the player can do most of the fighting but still have enough troops to call in for help. I don't do this all the time, but it's a neat method.
Long story short, you just need to play around. Go in the SP editor and use the snippet I linked and then in game run it and fast forward x4 (+ button) and watch for a few hours. After about 1 hour (game time) you'll have a decent snapshot of the landscape. I like to go 2 hours minimum before actually playing, but the more the better IMO.