After a bunch of searching and video watching it looks like a urethane liner material is the way to go. #2 in popularity was spatter paint (done it) followed by a body color paint (meh). In keeping with the theme of the car I think the Raptor black suggested by 72bluNblu gets the nod. I won't finish the trunk until after the exterior gets painted because the dry and wet sanding stages will get primer dust everywhere. For now I think I will shoot the trunk floor black so it's consistent with the rest of the car and move on to the next project.
