Foremost, this is more a matter of visual ability on each eye isn't it? I'm right handed but fire shouldered weapons left handed due to seeing better with my left eye. Took just a few hours to get comfortable with it.
This is absolutely the case. I am extremely left-eye dominant. When I can use my left eye for shooting, I can shoot equally well with either hand. (This only really comes into play with pistols or a long gun with long eye relief optics like an Eotech or Aimpoint.) Rifles with irons, it's left handed operation only, for me.
3. Keep left hand in place to hold rifle, operate bolt with right (rifle barrel will of course dip each time, but should be no problem when having something to support the weapon on).
This is exactly how I do it.
I disagree, i have a Mosin and have fired Mosins. They are renowned for their "sticky" bolts which a lot of the time is hard enough to do with the right hand, let alone the left.
Not a problem unless you use lacquered ammo with one of the heavily cosmolined rifles that wasn't cleaned properly.
From what I know about modern militaries, often they do not. You are just handed a right handed M16 and learn to use it. At least that's what i'm told it will be like for me in the IDF.
That is basicaly it. I know the M16 and its family of weapons can be operated left handed, I'v done it. The only real down side is the brass ejection is aimed more or less right at your face when you use the weapon left handed.
M-16 / AR-15 rifles are remarkably easy to use left handed straight out of the box. You can, however, get ambidextrous safeties, bolt releases and magazine releases.
If you contact the factory you can get an M16 or one of it's relatives to be made manufactured for left handed operation.
You can get lefty AR's from Stag as a normal-stock item in a lot of gun stores. Special order is an option, otherwise. The price difference is about $40, but frankly even speaking as a lefty I can't imagine using one. I'm so used to using a normal one left-handed that it just wouldn't work for me.
Keep your top button buttoned. Don't want to get a shell down you shirt. Heard that can happen quite often for lefties.
Not really that much of a problem, even with an AR that doesn't have the brass deflector. Mine is an A1, and I've never had a problem with brass. Now, my old Kimber 1911, that was a different story. Brass from that would go down my shirt all the time, but it didn't make a difference between left and right handed operation.