Might be pricey, but here is my suggestion. Figure the scale of the car to the model for digital pictures. In other words, how far from the car should you take the pictures. Get all views of the car. Then, in your computer, open them and print on paper to fine tune to the model. When they look to fit, print them on decal paper. For compound shapes you may need multiple decals (for pie crusting or compounding). Apply the decals as close as you can to the real car.