I used enamel, same as the wheels. Just rustoleum Regal Red...
The more I think about it, the more I think an ink (brayer) roller with no wooden frame and a little tape around the area would have worked better.
I spent some time with q-tips and denatured alcohol cleaning up so it's not a perfect method.
I wonder what the factory did? I can't imagine that they would spend the time taping or even using an adhesive mask, and I bet they rolled it as they probably would not take the time to mask off the rest of the tailgate/hood so it could be sprayed....