Never painted MDF terrain before, so was a bit unsure on how to proceed. But my Googlefu skills pointed me in the right direction I hope. Anyway, I got rather pleased with the end result at least. Started of by giving the terrain a base coat of watered down PVA to stop the MDF from soaking up too much paint. Two coats of blue, varnish and done!
The fact that I spent my youth playing Warhammer 40.000 2nd Ed might have something to do with the choice of color here. Blue seemed like the most logical color for an old space port.