Do you have link to the slickmod tints as they are precut?I purchased the Slickmod tints for the rear side markers. They were accurately cut to fit and I applied them (off the car) without a great deal of drama. They look good.
Doing the taillights (on the car) would be a step up in difficulty. A considerably larger area gave me pause. But the tints are cheap and if you mess up they can be easily removed.