Well...
I figured in the war it was applied with a broom (or at least in the sources I have read it was this way)....so I figured the messier the better
I used a regular paintbrush (of course at the time I didn't actually own an airbrush)....and the Crayola stuff is pretty watery to begin with so I just applied it.....waited a while for it to mostly dry...and then used a handiwipe to pull some of it off the high traffic areas....
But you might want to wait for others' replies before you just go with mine....
Here's an IPMS Stockholm article on the subject:
http://www.ipmsstockholm.org/magazine/2000/06/stuff_eng_tech_winter_camo.htm