Not an expert on driftwood but I can share what has worked for me in the past... first of all make sure the wood is old and hard, I have found pieces that have turned soft within a couple of days in water and you definitely do not want to be bother with that. Once I have found the "right" piece, I pressure wash it well and put it in the oven on a low temperature just enough for it to get very warm but being careful not to burn it with too much heat and bake it for about 2-3 hours. I then I dunk it in a bucket full of water for a few days to see how it reacts to being submerged, check to see if it stays hard, also you might want to change the water every couple of days, I do this for about a week or two or more till it stops releasing its tannins and its pretty good to go after that.
Hope this helps