Mine was all just working with them, and adapting techniques that I've used with other birds over the years.
I don't know that there's anything all that different in training a macaw vs. any other large parrot. (Other than the fact that they're at the high end of the birdie manipulation scale.)
These birds are so attention oriented, that if you turn it into a game, and playtime, you can teach them almost anything. If there's a big secret to macaw training, then that would be it... not exactly a secret...