Hi Coffey
I have used saltwater driftwood for my freshwater tanks too. I kept them out in the rain for a few weeks, then into a bucket that I changed the water out for a few weeks. Then into the sink for a good scrubbing to get any sand that may have been stuck in any crevices out. Then I put a pot on the stove and brought the water to a boil. Then I added the driftwood piece, if it was too big I would turn it over from time to time. I turned down the burner and let it go to a very soft boil to simmer for about 25 minutes.
Gave it a good rinse and then after it cooled down, added to the tank.
