I don't wear any kind of t-shirt under my regular shirt to separate me from the gun in my bellyband. I stop rust by coating the gun with a thin layer of oil, and that's worked well.
There are some good snug-fitting t-shirts to put under your top; UnderArmor makes some, and there's others you can find in the athletic apparel section of a clothing store. The synthetic material keeps sweat lodged in that layer so you won't see icky wet armits and that sweat line going down your back. :biggrin: And if the sweat is staying in that layer, it should be staying off your gun.
There are some good snug-fitting t-shirts to put under your top; UnderArmor makes some, and there's others you can find in the athletic apparel section of a clothing store. The synthetic material keeps sweat lodged in that layer so you won't see icky wet armits and that sweat line going down your back. :biggrin: And if the sweat is staying in that layer, it should be staying off your gun.