With tracks I have two different approaches depending on if they have rubber track blocks or if they are solid steel tracks.
Rubber Treadblocks - I base coat the entire track in flat black. Then brush gunmetal onto any of the track parts that are steel. I then drybrush with rust followed by another drybrushing of steel to highlight. Then I burnish any metal parts with graphite. I then finish weathering with pastels after the tracks have been installed on the vehicle.
Solid Steel Tracks - I start with a basecoat of gunmetal. Drybrushing, burnishing and final weathering is the same procedure as above.
I use Tamiya Acrylics for the most part with a little Model Master Acrylic thrown in for detail painting.
Hope this helps a bit Steve.
Happy Modelling and God Bless
Robert