A method calls for a rinse in 70% ethanol and progressive rehydration for a transition to water-based treatments. What are they specifically calling for? A wash with 50% ethanol, 30%, 10%, 5%, water?
As long as I know about surface sterilized using ethanol 70% is don't immersed explants for long time. You just need 30-90 seconds, especially for stem explants. And how we do rehydrate for explants that to late on ethanol solution? You only need to rinse it in the sterilized water. After that, cut of the necrotic part of explants then planting into culture medium. Good luck