Sighted braille teachers can read braille visually, even upside down, so they can read what's coming out of the student's brailler in real time. I had at least one teacher who could do that.
But of course, that's a specialized skill. To judge for yourself how conducive braille is to visual reading, when presented as black on white (or the opposite) instead of raised dots on a page, you can grab a braille font here:
