Purity: Order of Applying Camphor
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 574:
The recommended precaution is that camphor should be first applied to the forehead of the corpse; after that, there is no particular order in applying camphor to the other parts of the body.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)