I print these with a base just under the 100% solid areas, and then the glow is just halftones on the same screen as the colors.
So I would do
1 ) Base (under blue and white for the square)
Flash
2 ) Blue (with halftones, and a high opacity ink)
Flash
3 ) White (in the solid square)
I think they end up looking better with a less opaque glow than what shows on the screen, so that from a distance it looks more sharp than blurry, and as you get closer you see the glow better.
Another thing you could do is discharge white and blue, but I would scale back the halftone opacity quite a bit as the discharge doesn't sink into the shirt like plastisol halftones on no base. I would print this with a discharge base personally, and plastisol on top as I think for neon the plastisol lends to the effect.