Metalic colors cover everything. So, it's not you!
For metals, like in this instance (I use MM Metalizers), I start with "burnt Iron"...nice and dark...then fill in/highlight areas with lighter colors...Steel, Aluminum, etc...leaving a little bit of the darker color where I want it. A very fine airbrush helps. Mine will spray a dot, about an 1/8th inch, sometimes a little smaller. Low pressure and very close to the part....very steady trigger finger!