Also being ex-military, I've done a fair bit of breaking in of boots, going back to the '70s when we were issued those dreadful DMS (Direct Moulded Sole) ankle boots that led to so much foot rot in the Falklands (can it really be 25 years ago this week :AR15firin )
My method for the DMS ankle boots was to stuff them hard with newspaper, cover them in a thick layer of Kiwi boot polish and then beat the living daylights out of them with the rounded end of a ball-pein hammer until they were soft! Never had a blister from them and I covered some high mileages too!
After them, came the first general issue high leg patrol boots (the ones with the cris-cross tread pattern). Always wore those "straight from stores" and never had a problem.
Then came the current general issue "Britton" assault boots. These responded best to wearing them around the house for a couple of days, then soaking them overnight and walking/wearing them 'til they were dry and then doing it again.
Now that I'm out of the military and in the Old Bill, I wear the issued Magnum Patrol ankle boots for work; ABSOLUTE RUBBISH for walking in, but adequate for driving duties and general wandering about. Didn't need any breaking in as they're so soft, but the standard footbeds were pants and I replaced them with Sorbothane insoles.
Current walking/hiking boots are leather and made by Scarpa. Can't remember what model they are, but compared to the old DMS boots, they're like carpet slippers! Still tend to wear my old assault boots when the weather's really wet.
Overall, I've been really lucky and never had a blister from boots. I put it down to careful selection of the correct size and ALWAYS wearing TWO pairs of socks, a thick pair over a thin pair. That way, the friction is between the thick and thin socks and not the sock and the skin of your foot.
Be nice to your feet, you only get issued one pair!