Dry heat or steam works well for dry white oak, at least it does for our true white oak Quercus alba.
But now that it's been soaked and had boiling water poured over it, unless you sealed it really well before doing it, I would steam it. If you dry heat wood with a lot of moisture in it your asking for it to crack the wood as the water in the wood expands from the heat.
Good policy for most woods is steam for green/wet wood, dry heat for dry/cured wood. Now that the limb has been wrapped in a soaked towel for a day and had a bunch of boiling water over it, it is probably far from dry.