Do experience with this, myself.

Maybe you've already done a web search and found the link I'm pasting in below. When I read your posting, I remembered finding this page while searching for something else a couple of weeks ago. This is talking about big bins at elevators and such, but there may be some points that will be useful. The part about using water caught my attention.

Good luck. Down here, the worst kinds of fires (in ag) tend to be when cotton bales catch on fire. You've finally got to take them apart and soak them with water, and even then they may smolder for days.

Good luck. Here's the link:

http://www.grainnet.com/info/articles.html?type=go&ID=7000