Hummmm, got me thinkin' i tossed together a quick kludge of some thoughts for your "non"plugin method...

First make a layer and run the "clouds" filter (Filter --> Render --> Clouds)

next run the "difference clouds" filter (Filter --> Render --> Difference Clouds) on the same layer.

Open the "levels" (Ctrl+L) and slid the white slider to the left, watch the "veins" form, if they don't look right, cancel and run the "difference clouds" filter again (Ctrl+F will run the "last used" filter)

experiment with this until you get some good veins...

next duplicate the layer and invert it (Image --> Adjustments--> Invert) to give yourself a black sky and white veins.

go back to your other layer an change the "hue & saturation" (Cmd/Ctrl+U) Click "colourize" and play with the hue slider to change the colour. You may also want to adjust the saturation a bit. Make sure that preview is checked.

Select the "magic wand" tool and click on the white area, while it is selected, select the remaining white areas by choosing "similar" from the menu (Select --> Similar)
hit the "delete" key. now your layer only has the coloured veins.

duplicate this and change the "blend mode" to Overlay and run the Gaussian Blur filter (Filter--> Blur--> Gaussian Blur) making adjustment to suit your needs

you can duplicate this layer again to strenghten the glow effect...

you can also clone segments to add additional veins/bolts...

this is just an idea that may work for a "by scratch" - NO PLUGIN used method...
hope it helps

:)
retrocity