Anodizing works as follows:
1. Take the MacBook apart
2. Clean it
3. Chemical bath to remove old anodized layer
4. Clean it again
5. Chemical bath with power supply attached. applied voltage+current and duration will determine hardness and thickness of the anodized layer.
6. Clean it
7. Dye it.
8. Seal the dye in a hot water bath.
It’s fairly straight forward to do.