Folk like Doc Watson manage even though they can't see the guitar at all. One thing I noticed when watching Doc play onstage with others, was how little his fretting hand moved. He raised his fingers just high enough to allow the note to sound, which allowed them to come back down easily in the right place. (I've no doubt that the persona above who plays mostly with eyes closed does something like that.)

I play whistle & recorder and it is a good practice there also.