After experimenting with several methods of putting the correct amount of moisture back into the wood I have achieved success. If you have some Basswood that seems to be too dry, give this a try. Select several pieces that you wish to carve. Place them in a Zip Lock bag with a damp paper towel and seal it up. Let this sit for about 12 hours.
I found that the Basswood from the sealed bag was rehydrated to a point where it was easier to carve and held detail very well. You may have to adjust the amount of time and wetness of the paper towel to the amount and size of wood you place in the bag.