how do get model to look weathered?

You weather it.

Ok, what i do, is that first i apply a prymer coat, i use Gunze Off White, then the first coat of color, for example if the plane is olive drab i mix olive drab with white to "scale" the paint ( ex. 10 drops of white for 90 of the color ) then i use a very diluted brown color or black and airbrush it on all the panel lines, i use like 5 or 7 psi to paint a very thin line over the panel lines, after that i again use a very diluted olive drab or whatever the color is and airbrush it over the plane but at much larger distance so that the "fresher" paint does not totally covers the black one. the contrast of the darker paint in the panel lines and the clearer one over the panel will look like a real faded if you have some extra colors, you may use a brownish color over the top of the plane, you know the parts that are directly hit by the sun light. Remember, never be affraid of trying something new, perhaps it will take you some time, but be cool, get pics and practice some, you will be fine, and if you need something else, i am always glad to help!

My best regards
Hector Reymundo

I build aircrafts

Do you build planes, tanks cars boats or what?? please be more specific...