While I don't have any military vehicles to work on,
I do work on a lot of rusty old stuff at times. A North full face mask with screw on HEPA/vapour filters is a must have. Protects the eyes and face, and neck to some extent when you're looking downwards, while keeping the nasty particulates and vapors out. Putting on separate face mask and eye protection is a nuisance, but the North mask with ear defenders or plugs can be taken on and off in a moment. Heavy welders type gloves are a must have with rotary wire brushes, which I use a lot. A leather apron is a good idea too. At 9000 rpm those wires will go through a pair of Carhartt double thickness dungarees at times.
The "zip disks" or 1/16 cutting discs are another favorite tool and they can kill if they break in use. Someone had his femoral artery cut by one a year or two back and bled to death. A leather apron would have prevented that. It's a good idea to keep your head and shoulders, and preferably you whole body, out of the "plane of rotation", because if they break that is the direction in which the pieces are going to fly out.
The neck is an area that doesn't get enough consideration. One of those wires from a rotary brush could easily penetrate an artery in the neck if it hit the right point. That's why I like to keep my head down when using them.
At least have an old furnace fan going to blow the dust away if no mask, or just do like the old fellows did, and hold your breath! That's all pretty obvious
stuff, but we all forget at times and it took me some years to learn the hard way.
Wise to get a Tetanus shot too. The disease is still about 50% fatal if I remember correctly.