I don't mean to confuse the issue but I'm left-handed but right eye dominant. I shouldn't be good with a shotgun but I'm quite a good bird shot. When shooting handguns with the usual arms-extended-stance, I'm left handed again but use my right eye.

I'm just an example of one that shows that without formal instruction and advice in the beginning, I learned to compensate and be successful despite doing everything wrong.

I agree with Tom though that the best way is starting him out right (meaning left grin).