Weather with streaked paints or pastels

What kind of streaks?  Oil?  Exhaust?  For any kind of liquid (oil, hydraulics, fuel) I'd use oil or enamel paints.  For exhaust I'd used pastels or paint it on with my airbrush.

They can both work, so I don't think there is one "best". What technique you use will depend on the type of streak that you want.

I am currently writing a series on my club's website about weathering. I'm currently writing about oil paints, and the next article will be out in a few days (in which will cover streaking and exaust stains).

www.ipmsdayton.com/.../weathering-art-supplies-introduction

Depends on the paint.  Some paints are good for weathering, some not so good.  I know several friends that weather with watercolors, because they can be wiped off completely if you do not like the effect.  Don't do it with fast drying lacquers.

Is it not better to use a thinner thinner than that for watercolors for streaking?