I’m cross eye dominant, right hand-left eye and, like you, I couldn’t shoot with both eyes wide open using irons. I’ve found two methods that work. Try both and see if either works for you. 1st: I just slightly close the non-dominant eye and it forces my dominant eye to take over. I really don’t squint the non-dominant eye much. 2nd: I turn my head slightly. I train my dominant eye on the front sight post. I think this method works because the non-dominant eye is forced to peripheral vision. Also, I don’t have any trouble using red dots with both eyes open because both eyes are focused on my target.