Looks good! Subtlety is the key, minor variations in tone and color can make a big difference.
You may want to add a bit of dust and dirt in the form of pastels- shades of black, tan and grey.
I built this Mustang a few years ago and weathered it as if it had seen just a few years of regular service. I used paint washes and artist's pastels.
You're off to a good start! Research and look at pictures online to fill your mind with the natural patterns of dirt and rust that occur as chassis age and soon this will be second nature to you.
David G.