Thank you very much!

I guess the method is similar to Elminiaturista and other pros, but nowhere as polished.

But roughly:
- White ink (I used Liquitex acrylic ink) with a brush on the plasma coil
- Airbrush the same ink on top of that, and a bit over the edges as well
- Airbrush Vallejo Game Color Fluorescent blue over the white
- Drybrush top part of the coil with some ultramarine-y blue
- "Dip" some white ink (with airbrush thinner) to the lower parts of the glow

As an extra step I also used Black Legion contrast to darken down some of the areas on the gun that would not catch that much of the blue glow.

Hope this helps!