Or for wooden hives I have had good luck spraying with motor oilhttp://forum.beemaster.com/index.php/topic,22093.msg169528.html#msg169528
Used motor oil works well and is about as cheap as your gonna get.Richard Taylor used creosote. I don't think you can buy it anymore though.
motor oil is not harm full to bees ? dave
I have my many kids take a brush and paint them.....while I am sitting inside, drinking coffee, and going through my bee catalogues. It is tough, but worth the effort....lol.