Just wonder what you people in uniform do? Any ideas or suggestions greatly welcome.
Suck it up and deal with it was the military way. If that didn't work you could request some new boots or socks. I know it sounds mean, but the military doesn't have time for whiners. They care about soldier comfort, but only to a point.
We used heavy wool socks which provided cushion when walking, though could occasionally rub your feet the wrong way causing irritation, but where mostly a countermeasure against the bitter Norwegian cold and wetness, cold temps routinely in the negatives and water practically everywhere in this humid country.
To prevent blisters and soreness try to not use cotton socks since they retain moisture easier which softens the skin and makes it easier to flex, crack and irritate. Anti-chafing lubricants and talcum powder applied to the feet can also serve as a prevention to help keep them dry and maintain skin strength.
New, better fitting shoes are always nice as well. The better your shoes are fitted to you, the less they'll move or rub your skin, which again, can cause irritation or tearing, the causes of blisters.
Tannic acid can help strengthen the skin on your feet via soaking them. Tannic acid is found in some teas. Might be weird to soak your feet in herbal teas, but it'll help strengthen and tighten the skin on them, which will go a ways to preventing the formation of blisters, which are caused when the skin weakens and tears or become irritated (similar to how poking or prodding one's face can cause acne due to irritation).
The military didn't really have any specific ways to deal with blisters, though the socks we wore helped with moisture (a common phenomenon in humid, snowy, watery Norway) and cold (another commonality) and our boots were fitted to us to help maintain soldier comfort to a degree. If you developed a blister you were encouraged to prevent it from opening by protecting it with substances like Mole-Skin, also a prevention method, and tough it out.
Inserts typically help with arch and knee support, putting less pressure on either and increasing their longevity, so I'd recommend you keep using them too if you feel they help reduce soreness after a long exercise. They aren't going to be of much use in preventing blisters and may actually be the cause if they aren't fitted properly, moving around and rubbing the skin on your feet repeatedly irritating it or wearing out the skin and weakening it.