I wish I could take credit for this but I got it off another sight and thought it was a good idea to pass along.
If you can find floresent green nail polish (Spencer Gifts and most stores around Halloween) dip a tooth pick in it and touch it to your front sight and each side of rear sights. Expose it to a flashlight for a minute and you are good to go. I've tried it and it worked very well. :D It would do well in a pinch for sure. Plus its not hard to take off or refresh.