Best treatment for hair restoration of an old doll

This question is for those who have done the three main (?) hair restoration treatments. Which is your favorite for restoring shine/silky-ness and eliminating frizz, and why is it your favorite? Are there any major risks I should know about before trying any of these on a 1998 Molly doll? Steam seems like the safest to me but I also want to consider what’s most effective.

Steaming Hot water dunk/boil wash Hair straightener

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