One of the things I found out when writing my medicinal plants article is that papaya is great, not just for whitening but also for treating acne. Eating ripe papaya helps clear acne internally but mashing some of the fleshy side of a green papaya and using it as mask will do it externally.
Some, on the other hand, juice the flesh and some of the seeds of a green papaya and put some on cotton balls and use like an astringent. It makes blemishes caused by previous acne light and less visible as well.
If you don't want the trouble though of having to prepare anything yourself, just use toners and soaps made with green papaya enzymes. Local products like YSA, Human Heart Nature, and All Organics all have organic papaya soaps. But still, do eat lots of ripe papaya as well.