Re: Developing courage
Well, quite a few of the early teachers in aikido have trained tanto-dori techniques with real knifes... That's a way but we probably shouldn't even attempt it these days.
Personally I think you can be "courageous" by being centered at all times. So things such as not forgetting to breathe and consciously releasing extra tension can lead to a calmer mind and therefore a seemingly courageous one.
As for the training, I think Aikido training can be used to build this courage, but only when there are strong and sincere attacks involved. If you freeze up, you get hit. Then your body would learn from it. Perhaps meditation can help as well, especially with proper breathing.