i experimented and found that squinting my left eye would force my right eye to take over...
My brother and I go to the same optometrist. This is the way our optometrist suggested to my brother to try shooting long guns as he is left eye dominant but has shot right handed for years. Don't recall exact conversation but the doc told brother not to close left eye completely, but to squint as that will still let some light into his left eye and he will be able to see moving targets in a better overall manner.
We listen to 'doc' cause he's an excellent shot and I don't think brother or I have yet to outshoot him.