A hammerless revolver would work well being shot out of a ziplock, as would any SA stored in one and removed before using it. That would eliminate the sand in the Glock issue too, nor would sand be an issue if the gun were kept in your otterbox.
However, I just can't bring myself to support the off person carry concept, too many bad scenarios and the term "irresponsible" easily come to mind. Gotta find a way to keep it on you, lock it in the car, or find a new past time.
"Courage is being scared to death and saddling up anyway." - John Wayne
.44 Special: For those who get it, no explanation is necessary. For those who don't, no explanation is possible.