Airbrushing a Nebula

First post, might as well post something worth looking at beyond a "Hello world."

The FLGS I usually haunt was recently putting together some boards for X-Wing Miniatures.  The initial plan was to take some 4'x3' (6" for player cards and tokens on the ends) MDF boards, spray them with black spray paint, then put stars on them by loading a toothbrush with white paint and flicking the bristles.  I offered instead to try my hand at painting some nebula effects with my airbrush.  Worst case, we'd respray the boards.

I skimmed a few Youtube videos, then plunged in.  The initial layer is Vallejo Grey Surface Primer (white can be too bright), and I simply painted a monochrome cloud effect:

Many airbrush colours are too thin, and will just vanish on a black surface.  Instead, they are used to tint the monochrome layer, like so:

After that, some careful addition of bright points of light for stars, and a satin clear coat to fend off some of the wear these boards experience:

A second board soon followed, a little more ambitious.  The effect I was going for was a space storm:

And coloured:

There's still 2 boards unpainted.  Some kind of black hole is at the forefront of my inspirations.  But the 4th board I'd like to try to create a Death Star Trench Run, working up some mix and match stencils to paint a simulated mechanical surface.