My question is are you trying to simulate metal by painting plastic track or are you asking about actual metal tracks ?

Panther1/35

can I just airbrushing metal track or do them have to be burnish. post it aginst here besuase I am not sure if this is a general modeling question or an airbrushing question 

 

 

Your in the right spot,either way works good,I have used burnishing liquid,but it ain't cheap.you need to do it just right,scrub the tracks with acetone,and work it into all of the crevices,but if done right lt looks good.

The last few that i uaed,I prefer to paint and weather them as if they were plastic tracks.