Agree, every situation seems to vary some depending on the particular wood and the time its been dead and the conditions it was under. It might be easy or it might take longer. I found a great looking piece of wood this weekend just past and I went looking for a large white plasic "paint bucket" (I was picturing one of those large commercial type used buckets but I found even the 5 gallon ones to be a bit too small in the dimensions.) I then realized I could use one of those large rectangular "Rubbermaid" plasic storage boxes like I use to store things in the shed. It was plenty large enough to fit the wood and had a cover to keep bugs and leaves out on the back patio. What I'm doing is planning to leave the wood submerged in tap water out there for however long it takes for the tannins to go away. I pour boiling kettle water over the wood whenever I have some extra time. If it takes a few weeks then so be it! The two things I'm trying to accomplish are to see that the wood no longer brews up a yellow color in the bucket water and that the wood has absorbed enough water to hopefully stay down on the bottom without me having to attach a rock base to it.
~~waterdrop~~