Breath work is one of the most powerful practices you can do and is woven into many systems but IMO it's best to focus on it by itself rather than learn it in the context of a martial art or other movement system.
The practice i would recommend most is learning to do a 20 second breath, then 30 sec, 40, then 1:00. The practice is simple: inhale slowly and evenly for :10, then exhale slowly and evenly for :10, repeat for 5:00 to start with. As you get better, go for 10:00, 15:00, etc. As you get deeper into the practice, start working a :30 breath (:15 inhale, :15 exhale) into the practice about 3/4 of the way through your meditation period. It's actually easier to do once you've relaxed a bit instead of doing it right at the beginning. Never move on to a longer breath until you can breath evenly and consistently with the breath you're on. going too fast is the number one mistake. When you eventually get to the point that you can breath once a minute, your meditation practice will be able to go very deep.
When I did this intensely, almost nothing could angry me. If you're high strung, this is for you. By controlling my breathing I could detach myself from most anything because the breath and the emotions are connected.
The problem with this method is that it's too simple for some folks and you can't make a DVD or write a book around it so you almost never hear about it. People want bells and whistles and this doesn't give it.
Try it out for a while and let me know what you think.