First, the disk must be very carefully cleaned and washed. You even need to use a toothbrush, washing powder, soap, detergent.
But that's not all. Before painting, you must accurately grind and Polish chips, scratches, fender paint, and other damage to the coating. Than sanding and polishing – you choose. Importantly, the surface is efficiently cleaned and polished. At this stage, as corrected and more serious damage of the disk (scratches from the pads, dents and so on).
Then clean your cast disk from dust and other residue that formed in the process of Stripping the surface and degrease. This can be done in any solvent. After using degreasers install the drive on the frame or something resembling it (e.g., bucket).
You can now proceed to the priming disk. Four pieces will take about a litre of primer, if the cover disks in three layers. Don't forget to grind each new layer of primer, before applying the next (where required). The paint should be applied also in three layers. Using the spray paint, keep in mind that you need to find the optimal spraying distance so that the paint did not go bubbles and did not spread. About 50-60 cm will be sufficient. Each new layer of paint with the appearance of drips and bubbles you need to clean up. That will fit fine grained sandpaper.
After painting and final drying of a lacquer. It also should be applied in three layers. As you can see, to paint the molded disk is not difficult, it just requires a fair amount of patience. However, you can save some money.