Holiday? I'm Australian so not for me (though I do get Queens Birthday off in a couple of weeks
).
If you are making cement, what you can do to get a texture is to mix a batch of grey paint in a tub with either ver fine sand (very being the oprative word), or something like Harpic (caustic soda - pot and pan scouring stuff) until you get a 'gritty' feel to the paint, then slap it on. It should give you a textured surface. Polyfiller also works, but gives a smoother, more wavy texture.
Unfortunately I don't have the DD comics, but guessing form the general description, a piece of clear plastic sprayed white on the reverse of where people will be looking should give a skylight effect depending on the lighting. To make some panneling, simply attaching a thicker, differently coloured piece of cardboard can work to make a panel or bit of scenery. Fly screen (the mesh, not the woven type) can be sprayed and used for vents - I've used the net stuff apples come in, pen lids, pieces of old watches, badges and all sorts of other stuff in various projecs, so there are alot of things that can be turned into other things.
Masking and spraying would be best for laying down guide lines on the floor and the like. Violentfix has a tutorial on how he made his hanger on his site, so you could have a look how he did his too.
http://www.violentfix.com/cobra/dio...on/airfield.htm
Hope that helps