When I was in my '20s and '30s I shot in NRA match competition. They shoot one handed like the military trains you. They allow scopes apertures, special gloves, etc. I tried a couple of these and to me the difference was marginal. Your initial reaction is "gee, this is great". I think it is a lot like golf. When you're not doing well, you tend to think new equipment will help.
Today I shoot two handed with both eyes open.