I played with this a couple if years ago. I made a fermented extract with LAB and the whole plant here in this post.
And in the bottom of this post I took the root and peeled it, then used a zester to grind it down. I let it dry, then filtered it through a 120 micron screen. That left me with a powder similar to what Meesh is using.
If I were to do it again, I would chop up the root and soak it in vegetable glycerin for 90 days. I did that with some reetha and it worked great.