1) This is a tutorial for making chaotic structures using the brush tool. To begin you need to make a color layer in white and a second normal layer over it. Select it and continue.
Select brush tool and set the presets like this selecting a simple round brush

Then like this (shape Dynamics); (Scattering); (other dynamics)

Make some random brushing changing the brush size; change opacity to 20%, make a new layer over it and repeat the last step but trying not to cover the last brushing.

Now change opacity to 50% and repeat the last step.Change the color of the color layer you made at the beginning to black and set outer glow like this to the three brushing layers you made.

Finally you can add an explosion in color dodge blending mode and change the color of the first brushing layer's out glow. Experiment. (_View final image_)