edit: I don't remember where I have this idea from, and it may be stupid, but it kinda stuck with me: if you can't find out how to solve a problem, try to find a way to make it worse, as that can give you hints how to overcome it. I have no idea how this could be applied to anxiety, not in general and of course not to yours; or wether that's a good idea even (surely might not be without friends or professional care around). But since you said you're all out of clues I thought I'd mention it anyway, even if it's just to bring people "out of the woodworks" which will tell me why exactly this is a bad idea (I really have the feeling it might be). I'll simply trust you'll not go off and do something dangerous with it; but maybe you can reverse engineer it a little that way.
Some other things that helped me a lot were to just tell my friends up front that I felt like I was having a panic attack. You'd be surprised how little amount of other people will judge you for saying it. Most people offer up advice and feel sympathetic, so telling them usually helped me calm down. I also went out and bought a bicycle and a basketball hoop. When I was feeling like I might have an anxiety attack, I'd just go outside and shoot a few hoops (I suck at sports, it was just something to do), or I'd go ride my bike around.
I did try herbs. I never took prescriptions. I don't think herbs every actually did anything, but sometimes it felt good to just be "taking action" and they had a placebo effect in that sense, I guess. That's just me, though.
Also, I take stuff really personal usually, and I'd bottle stuff up. I used to get very frustrated when something I'd been programming on for awhile hits a snag or I can't figure out how to do something, despite weeks of Googling and stuff. It may sound lame, but sometimes it felt really good to just let it all out. Whether it was crying or yelling or whatever. I had one time driving home from work, having a panic attack, that I couldn't handle it and I just started crying for some reason. It felt great after. I had other times where I'd just yell in my car and that'd be enough to kind of derail an anxiety attack.
I don't know man, I don't think there's really a 1 size fits all solution to anxiety. It's just finding something that you can use as a tool to help yourself get through that 1 moment in time. Don't look at solving the whole thing, just look at solving each panic attack, and then use those tools to get you through 1 day, 1 week, 1 month, etc.
The rubber band thing works because it interrupts the usual pattern of feedback loop where the anxiety builds and feeds on itself.
You mentioned breathing. You are talking about deep, yogic breathing? This is where you engage the diaphragm, ribs, collar bones, breathing smoothly, deeply, and quietly.
In any case, I found that anxiety, like procrastination, is the symptom rather than the cause. Anxiety arises from deeper issues. Those deeper issues are addressable.