Actually there was an articlle a few years back on making airfield and strips (in FSM i mean), I remember the autor used (here is my English starting to fail) cat-litter-filling, or however you call that stonelike stuff you put in that thing where your cat does his...
The other items used were an empty bottle to roll the litter-stuff (mixed with glue I suppose), and seringe where you put in black artists' oil or acryl in, however you will need a muscular seringe, not a sub-cutane, because of the thickness of artists' paints.
The litter, rolled out looks like tarmac, and with the seringe you make the tar-joints, so no airbrush, or whatever is involved in this operation.
I remember also that in the article thay also spoke of the shape of the tarmac joints, I know there is a big difference between Nato and Warshau airfields concerning those joints, but I don't remember.
It's certainly worth looking in your older issues of FSM.