Vinyl Tracks

I don't prime my tracks, but I do paint them with acrylics, which seem to adhere better than enamels.  The process I used on my T-34 which had silver vinyl tracks was to spray a base coat of ModelMaster Acryl gunmetal.  Next, I sprayed on ModelMaster Acryl rust.  How much depends on how new or old you want the tarcks to appear.  I then applied a dark acrylic wash. (Actually, the first time throught I applied an enamel wash which lifted the paint, curled the tracks, and apparently ruined everything, so I had to scrub off the ruined paint, straighten the tracks under warm water, and repaint!)  I added a little bit of mud and dired on dirt in the form of ground pastel chalk held by a flat acrylic (4 parts Future + 1 part Tamiya X-21 Flat Base).  I sprayed on some light browns, Tamiya buff and a darker color, to simulate dust and dirt.  Lastly I drybrushed silver here and there to represent wear.  For the dry brushing, I didn't worry about the paint being enamel, because so little was applied.

On the other hand, newer armor tracks are usually made with a vinyl that may be glued with conventional glues and painted with enamels so check your instructions.  The aforementioned T-34 was an early 1970's Tamiya offering.

I used to have problems with paint flaking off vinyl tracks, no matter how carefully they were cleaned or what paint I used. Someone here (sorry, can't remember who) posted that they used artists Gesso as a primer for vinyl, and it works great! This stuff will stick to most anything and can be thinned with water for airbrushing. When dry, the tracks can be bent double with no sign of cracking and paint adheres to it very well. Since then, it's been my primer of choice for anything vinyl.