I've painted the front sight on a number of snubbies, and find it very helpful in low-light conditions. A tip: after thoroughly de-greasing the metal, apply an undercoat of WHITE model paint, and let it dry. Then apply the fluorescent red/orange/green on top of the white paint. It dries to a much brighter color than if it has the plain black metal underneath.
As for the rear sight, I agree with Bluesbear that White-Out is a good way to go: however, after a few tries, I just left the rear sight alone, and did the front sight. At snubby ranges, you're trying to acquire the front sight as rapidly as possible against the center-of-mass of a close-range attacker. You really don't need precision sight alignment - just a coarse sight picture.