If the brush is hardened from BIN, it's trash. Even if a quality brush, the time and material required to clean, and the inferior brush you'll have after, make this effort an actual loss. I work with BIN on a regular basis and have never once used denatured alcohol. Well, maybe the first couple of times, until I got smart. Firstly, if you wrap a BIN brush well in plastic it will last for months. Usually you'll find one wrapped in my gear to do spot priming, which then gets re-wrapped for the next time. Secondly, ammonia is excellent for cleaning BIN brushes. One gallon of ammonia is a few bucks, one quart of alcohol is around ten, you tell me. It didn't use to specify ammonia as a cleaning solution on the can, that's fairly new wording.
Poppameth, I experience no pain, other than the smell, when using ammonia. You need to change up, you're working too hard. Ammonia is much simpler/less work than alcohol.