The lens tint spray is a little tough to get even- I would suggest practicing on a scrap piece of glass or clear plastic first and play around with how many coats to get the darkness you want.

Either way- go with really light, multiple coats with it...

 

I've had practice, I did my tail lights to.

 

Let's see those tails, red. I plan on doing mine at some point but not until I get my berger panel painted black.