Yep, I use a Chapstick on the inside of my left lens with some frequency these days, being an old untrainable rightist kinda person. It works but I would be better shooting from my left shoulder when tired and the left eye takes over, but WTH, it never forewarns me when it is about to do that ... I always have a 'perfect' sight picture .. and that of course is the very crux of the problem.
Having a dominant eye makes it a very simple matter. Neutral vision is a bit harder cat to skin. It affects a VERY small percentage of people, something on the order of substantively < .2%, so I am told.
The suggested grease smear works quite well, thankfully.
