Were I looking to do any type of coaching unfamiliar to me, I would contact organizaitons that directly work in the activity. So, in this case I would contact Ironman.com to start. I believe they do have coaching courses or support programs. And contact local triathlete training programs in your area to see if they can offer you guidance. They may even want to include you in what they are doing or allow you to attend events for the purpose of learning more.
I work more with athletic development and movement correction of runners, swimmers and cyclists. The “where are you weak, out of balance, tight, loose, etc.” side of athletics, than the miles and hours end. But the above would be my first thought on what you are interested in doing.