[DISCUSSION] Cleaning soft plastic [Figuarts hands]

My GokaiRed Figuarts, who I had out on my desk for nearly a year, has some nasty yellowing on his hands. What would be the best way to restore the color as much as possible without risking the integrity of the plastic?



Everything I can find regarding cleaning pertains to harder plastics, like those used for Zords, so I'm just worried using something like isopropyl or baking soda might ruin the hands.