Still working on pre-req's! But to piggy back on the topic...
CURRENTLY doing it.
BLUF: Talk with your schools about your Non-Trad situation. Do your research for online classes. Study in the morning. Volunteer on saturdays. Network, network, network.
I had all of the biology courses and advanced biology courses completed in my undergrad. So basically I need/ed my Chemistry, Physics, and Orgo knocked out, WITH LABS.
I have my top school (THANK GOD) and basically any other school willing to accept online credits for admissions. These schools said that they would accept the credits due to, basically, the military being impossible for brick-mortar schooling. I study for 4 hours every morning before going in to work; because after work (much like working out), motivation can die. Especially with an 80hr work week.
For volunteering: I looked up clinics/hospitals on the Red Cross' website. If you're stationed internationally, this can be a huge advantage. It just so happens that a lot of military bases allow Red Cross volunteers at your on-base hospital. Maybe your hospital is actually open on Saturday mornings?
Need to shadow? Just start talking with your PCP! (Except I haven't yet.. ). Maybe take a day of leave. If your family/leave situation allows, take personal leave to maybe shadow physicians at a hospital for an entire week.
For LoR's? Hit up one of your old professors from college MANY years ago. Start that networking again. Snag a letter from the physician or PCP you had been shadowing. Maybe a letter from your volunteer organization.
For the MCAT? You've already started prepping. Every move you make.... every course you take, every step you make every breath you take.. umm.. Be prepping! With every class, incorporate one of them fancy lil' Kaplan books. Or maybe the Khan Academy.
Finally: REST! Maybe every Sunday. Just don't lay a finger on a book. Have fun.
Of course, I can imagine how much more difficult it would be if you had kids... Don't volunteer then; mention ALL volunteering at you've done with the military.. list ALL awards/decs. And shadowing doesn't have to be something that takes up all of your time. 50 hours can definitely be doable... maybe knocked out in 4 days, if done full-time.
And being healthy? Well... intermittent fasting saves money lol... But HIT saves time. Running 30 minutes can be pretty quick too. And a great social activity if you need to check that box too.
Okay, enough with the novel! Like I said, CURRENTLY in progress, but it is being accomplished verrrrryyyyy carefully..... lol