I agree with everything. Also the quality of the meat is very important. My husband puts on the fire (with wood of course) about 2 h ahead. Maybe not the right salt but the right amount of salt, the right height of the meat : it should go slowly, if it is too close it goes fast, it gets burnt and it is not well done on the inside, and you should have enough burned wood to last until the meat is ready. Burned meat is totally unacceptable : You never put flames under your meat.I don't know - I don't think it's as easy as people think it is having watched several friends attempt and fail. I think the key is a) using the right salt to rub on the meat before cooking, b ) building the fire and keeping it at the right heat and keeping the meat at the right distance above it and c) judging the amount of time it will take and putting things on at the right time.
I adore asados and luckily enough, live with someone who is a master at them. So I just appreciate the results and don't have to deal with the work
As for where to learn - find a friend (yes, 99% of the time a male friend) and ask him to teach you.
ETA - Using carbon to do an asado? Heresy!!!!
And David - don't know where you're eating but we always put vegetables on when we do asado. Roasted peppers, corn, potatoes and onions wrapped in tinfoil, etc.
After all these years my husband is quite a good asador, he learned it through watching friends, and then inviting friends over and 'asking their heip'. they will be happy to say that all you do is wrong, but in the meantime you learn how it is done properly; And then practice, practice and practice.