In ANY parabolic antenna, you are making a GOOD REFLECTOR. So the material should be as conductive as possible. Good antennas are made as aluminum molds or pressed of aluminum sheet to a precise shape.
Many people try to make molds of laminates; then covering the surface becomes a problem. The best is to use copper-foil stickers as described above. Aluminum stickers if used, need to overlap by 0.1" or 3 mm for good results. Conductive paints are often difficult and do not survive long time. Beware- aluminum paints often consists of small particles immersed in a glue- this does not work well as the particles cannot connect with each other, and such antenna will not focus!