Tips on whitening Obistu 1/6 body and parts?

As title states seeking a way to make the obistu 1/6 body pure white for my Catrine Demew Monster High. Any tips, tricks or suggestions would be very well appreciated.
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Where no dollieh is left behind.
https://www.dolliehsanctuary.com/sanctuary/
https://www.dolliehsanctuary.com/sanctuary/viewtopic.php?f=13&t=11719