Back when I bought and painted my Tau in 2009, one thing I didn't know was varnish. I learned about Dul Cote during my 3rd army, Blood Angels. So my Tau was unvarnished (I've also since refurbished almost all my Orks, so it's almost all varnished as well). I also needed a better way to designate my Firewarrior units.
So I made each one unique with shoulderpad trim and varnished them up. I've also varnished every single drone I have, plus the 2 XV8 suits I use in my current list. I've gone through a whole can so far, and only the Broadsides remain.
Combined with their nice and shiny new Guardian Drones, the core of the army is set to hit the battlefield. I'm actually quite stoked about how these came out.