Making spoilers can require extreme craftsmanship. You can make them out of a metal floppy disk door (the piece at the top of a floppy disk that's silver). You have to have pliers and wire cutters (or some other type of metal cutting tool). You have to cut out a strip about 75 mm wide. Then you bend it to your desired shape, glue it together and then you can paint it. Or to make it easy you can go but a “Hot Wheels” car that has a plastic spoiler and then use wire cutters to cut it off of the car and just glue it on to your modifier or apply however necessary.