The different services place rankings in different places, though the Army and the Marines tend to have similar placing. The air force tends to prefer to place every thing on the front of the uniform. I would guess that they could be easly identifiedon their backs. I am not familiar with Navy or Coast Guard markings. Sorry I can't be more help.
And to answer LemonJello, the easy way to paint that camoflage is to get a small peice of wood, cut it to scale in a square, dip one end into the paint (CAREFULLY! If you aern't careful, you will get too much paint on the wood. Try to just touch the end to the paint, and not get any on the side.) Though you could cut a sponge to the right specs, I don't reccomend that as the sponge tends to soak up too much paint. Anyways, then you just press the stick onto the model. Again, the amount of paint is crucial. Too little, and it will not cover correctly, too much, and instead of printing perfect squares, the paint will pool into a circle and run. Try practicing on a file folder, or a similar peice of thin paper. I found wax paper to be a good practice surface, as it does not absoub the paint very well, simulating plastic. Or prehaps you could use a practice model, or unused parts from an old model.