In my experience. It's nearly impossible to use the iron sights in near to total darkness.
The best you could hope for is close range point shooting.
However, with a tactical flashlight mounted to your AR the sights and the target show up perfectly with the light on.
I got to try this out for real the other night, when a skunk infiltrated our home(carport). There was very little light (moonlight) and I could not see the sights at all. When I flipped on the flashlight, I could see the sights perfectly and two glowing eyes looking at me. Well I lined 'em up and blammo, a perfect shot that couldn't have happen without the assistance of a high intensity flashlight.
BTW, I shot it with a 10/22 not an AR. [:)]
You still won't be able to see a painted tip and it will probably mess up your daytime shooting too.
A nice mounted flashlight is all I can offer.