I agree with Scott, but, I prefer to use SNJ metalizer paint. There are two reasons. This paint is ready for the airbrush right out of the botle with no thinning, and it is dry to the touch within 15 to 20 mins. and fully cured in a few hours, I have masked over this SNJ and it is great. There is also an accompanying polishing powder that you can get, so if you want differing shades of NMF on an aircraft you can polish to a high "chrome" or represent dull aluminum, or anything in between. Alclad is fantastic stuff, but, if you want to vary your panels etc., you've got to buy all the different types (and they're not cheap) and then mask and shoot individual panels with them.
Steve