A single nerite species won't really be found thriving in both brackish and salty water, the same as a single species won't be found in both fresh and brackish water. Most true nerites (Nerita species) live and breed in saltwater. These species spend a lot of time out of the water, though, dependent on the movement of the tides, and most can tolerate some exposure to fresh and brackish water. There are other species that are found only on the rocks at the mouths of freshwater streams, living in salty water where there is a constant flow of salinity-lowering fresh water. As you move up those streams and the salinity decreases, you find different species. Many of the Neritina species that are sold in the hobby are indeed brackish water animals, and consequently you'd need a tank with brackish water and grasses and/or mangroves if you wanted to try to duplicate their natural habitat. There is no need to try to slowly acclimate these type snails to lower salinity. For the pure saltwater species, you could do this and they'd probably survive, but it isn't likely to make them want to reproduce in your tank.
You might search for scientific papers on reproduction of the specific kinds of nerites that you want to breed. The required conditions may be very different, depending on which ones you want to try to raise. Disregard any generalizations in the popular literature about all nerites only breeding in brackish water.
Cheers,
Don
