i would use the rust powder for the streaking BUT BE CAREFUL. i think my rust powder is tamia and it looks really nice but stains the paint so you want to do a little at a time, just a couple of grains at a time.
i don't put a barrier clear between my acrylic paint and my powders or oil washes unless i have ALOT of decals i need to knock down the sheen on. my painting and chipping has decreased since i started doing modern vehicles. even exhaust systems on big trucks just don't rust. so it's mix my own dust with pastels or lots of washes.