Painting a Styrene bridge

[unittrain]

I'm getting ready to paint and weather my scratchbuilt truss bridge its mostly Styrene with brass lacing bars, just wondering what paint you would recommend , I don't have an airbrush was considering flat spray paint would need to mist it so as not to apply the paint too thick. My questions are do I need an airbrush (obviously would get the best results from one) also will I have to rough up the surface on the Styrene for paint adhesion? I'm considering applying archer rivets and was wondering if the N scale rivets show up enough to be worth the effort?  I plan on chalk weathering the bridge once painted.

[wazzou]

Valspar Blindfold from Lowe's yields a nice Grimy Black.  Just apply it in several light coats over a couple of days until you can get it fully covered.  The inside of the bridge may be a challenge.

[peteski]

I would make sure the styrene and brass are clean (free of any sort of grease or oil).  Especially if you were to use water-based paints.  If you use organic-solvent-based paints those are more forgiving.  No need to roughen the surfaces.

Spray cans are like really crude airbrushes - you have almost no control of the paint pressure, flow or the spray pattern.  I suspect that your bridge has a lot of tight areas which will be hard to get the paint to without flooding the surfaces around those.  That is where airbrush shines: You can easily adjust the paint flow, pressure and spray pattern to gently spray paint into those deep tight spots.   Then open up the nozzle and spray the outside surfaces.  This extra control the airbrush provides is the reason I often decant spray-can paint and spray it through the airbrush.

[engineshop]

For hard to reach areas and corners, use a regular brush. Not too thick but a nice cover. After that it only needs a light spray with the can to blend it nicely.
I did that with my container crane which is made out of styrene and brass parts, too.