Right handed and left eye dom.
With a rifle just shut the left eye or squint left eye slightly. (I have a coworker who can't blink or squint one eye at a time worth a damn, weird.)
With handguns I do the same or cant the gun slightly to use my left eye.
NOTE: I'm on the waiting list to get my eyes surgically switched.
Second NOTE: Doing anything left handed is an abomination.
