After it's dried to the point of brittle, break it up a bit by hand and dump it into the blender. Small batches works better than one big one.
That's after it's blenderized. If it's still feeling a bit damp, stick it back in the dehydrator a while. The drier it is the less chance you have of spoilage. Then just dump it in a jar!
Here's some persimmons that I dried and powdered the same way. Sorry for the blurry picture. We rehydrated it with 2 cups water to 1/2 cup powder. Don't just dump all the water in at once, though. Add it bit by bit to make sure that you don't overwater it.
We used this to make a great bread with, and tossed in some pecans and dehydrated figs too. Dehydrating is a great way to use up figs, especially if you have a ton of them. Cut them up with kitchen scissors when it's time to cook with them and use like raisins - they have a much fuller flavor than you'd expect. Even someone who won't eat raw figs or fig preserves (me) loves them cooked in breads and the like.