I have aged several beers in wood here at my brewpub. I have both French and American Oak. For the first use, before beer was ever in the cask, I did a cold water rinse to get any "chunks" out then I filled it with 200 degree water and let it sit for 1 hour. Of course, this killed anything in there. I then filled the cask with beer and that's it.
I have never cleaned my wood barrels with any detergents, and have been told in the past that this was fine.
I had very good luck with this Practice. Also, you should know that once the barrel was used a few times it starts to loose the big bold wood character and slips into a moe subtle note. All I do now is fill the barrels with 200 degree water, dump it out after about 30 minutes and then run the fermented beer right into it..
not hawaii...Martha's Vineyard