i put all my driftwood in large trash cans,fill with hot water(empty and refill every day)soaking in hot water works alittle faster,also purigen works very well for taking the color out the water,and it is rechargeable.
i have used this method on very large pieces and it has worked every time,longest i ever soak a peice was 3 weeks(large stump piece).
tip:use a few cups of marine salt in the hot water(seems to help)