I've been posting/reading on these forums for years, and what shooters use seems to vary from "Wite-out", to "Moon Glow" to model paints (for gasoline engine planes or model cars).
In the last year or so, a bunch of us have been experimenting with flourescent model paint -- which is now my preference. I use a mix of yellow, white and green to get an almost white front sight. The Flourescent works very well in bright light, and better than you'd expect in dim light. I prefer white-outlined night sights for all-round shooting, however.
Nail polish and model paint seems to resist most solvents pretty well. I would think that model paint covered by clear nail polish would do very well, indeed.