Something I've been looking into doing as well. Here's what I know
Most Neons come from fish farms, so they're pretty easy to spawn. They need soft and acid water. pH about 6.6 and hardness less than 10. They're egg-scatterers, so a spawning mop at the bottom of the tank, and one hanging from the top would help. Condition the pair seperately, and when the female is plump with eggs, put the pair into the breeding tank, and turn the light off. Make sure that the room gets NATURAL sunlight, but not on the tank itself. Indirect sunlight. Neons will spawn usually at dawn; when you see the eggs in the tank, remove the pair. They can and will eat the eggs. Then cover the tank with opaque paper, as P. Innesi eggs are really sensitive to light. When the babies are free swimming (~5 days), feed on green water, rotifiers, and "APR" (artifical plankton and rotifiers) or something like that the first week. Then to live baby brine shrimp ASAP.
That's all I know, but I'm pretty sure it's accurate.