There are several ways you can paint and weather Friulmodel metal tracks. That's how I did!
The picture below shows a set of Friulmodel ATL-54 tracks, still under assembling. They will be put on a Soviet SU-152 self-propelled gun (you can see it here).
Once finished the assembling, I made an oil wash on the tracks with turpentine and Mars black, followed by another one using Burnt Sienna. These will be visible especially in the joints, and they will be a strong base for the grip of the pigments I will apply later.
Once the washes have dried, but not completely, I applied some Track Brown Mig pigment, which adhered easily to the underlying oil color.
On the inner side, in order to simulate the wear due to contact with the iron wheels of the SU-152, I wiped the corresponding zones with an old stiff brush. On the outer side, instead, I rubbed the track treads with a finger, uncovering the underlying bare metal color, thus simulating the wear due to contact with the ground.
Finally I fixed the pigment with the Mig liquid fixer.
This is the final effect.