Congrats on your upcoming retirement! And thank you for your service.
You've already started! APC forums are a great plac to start. Before I went to Emerald Coast (I went to the seminar), I scoured this website, airlineinterviews_dot_com and JetCareers. Also, check out willflyforfood.
Don't discount wikipedia and the airline's own websites either. I wiki'd every airline I applied to, read their wiki page, googled them, read all the news articles I could and then typed in the airline name in YouTube. A lot of fluff came up, but check out all their CEO videos that are sometimes posted. On each airlines website check out their investor documents and read them. They have a lot of good info in there as well.
I'm not sure if you did recaps after each flight in the USMC, but in the AF, we did recaps after all our deployed flights so our DO could see how the flights went. I made copies of all of them, they were immense in remembering details for TMAAT stories.
Good luck and it's never too early to get your apps in and start looking for buddies who may be at those airlines.