some folks have had success with the spray on tint from VHT, that is used on plastic light covers and such, but in reality as you won't be "looking thru" the shortened shield, spray paint would do the job.
As for using the film type tinting, I was going to attempt it on my C14 shield, but when you take account of the compound radii that exist, it's a gamble, as the material doesn't stretch. You can however cut strips, and overlap them carfully, and cut and peel off the overlaps while its still wet during the application.
a rifle or C10 factory shield is pretty flat with regards to compound radii....
Use plenty of water/spray (2 drops of liquid soap to a quart of water works) and work on a good table surface covered with a couple towels for keeping the work steady.