Since no-one else has written a solution I guess I'll try.
Now apart from the obvious (take cover and headshots) there really isn't much else to say.
At the end after you shoot down the plane and save Jenny DO NOT take the helicopter as you'll have to play through mission 15 again (unless you've unlocked it previously).
Play solo as you'll obviously have a larger screen, You can have any of the AI heal you rather than solely relying on a co-op buddy and in the levels where it's just Kane and Lynch he can provide you some essential ammo resupplies.
The AI can be pretty decent so you can pretty much leave them to deal with the enemies.
If your struggling with a particular part in a mission you could always adopt another strategy, but all the enemies follow a certain pattern so it most likely wouldn't be necessary.
Compared to most games it's pretty easy for average players, will probably take around 4-5 hours and most likely cause of death is to OD in my personal experience.
Hope these tips help someone in need.