I have had success using the "dry defat" and thought it was worthwhile for me but it didn't pull a whole lot of fat out of powdered MHRB simply because there isn't that much in MHRB or at least, the batch of root bark I had didn't have much fat in it. However, for other kinds of root bark such as Desmanthus it will pull much more fat out but most people are not working with that plants root bark. Also, much depends upon how finely powdered your root bark is.
I believe the general consensus for MHRB is don't bother.