Yes you have to be full time and CLEET certified (not reserve). You also have to have a basic instructor development before you can even attend firearms instructor school and you can't attend BID until being certified for 2 years. After that it's 200+ hours of training with a 60% failure rate, then teach a full time academy as an adjunct before you get your red hat.
Thanks ... does not look like its doable for me since I would have to quit my full time job to do it. I was looking for coaching opportunities on my days off