I always wonder why this isn't a bigger part of the discussion. None of us would develop a visual UI flow without trying it manually at least once, but for some reason this idea isn't extended to discussions about accessibility. The advice always fits into these three groups:

1. Follow a checklist

2. Buy my software

3. Hire blind people to test your app

I'm not saying that these are bad (although some overlay software is actually worse than nothing), but aren't people even a little bit curious to try the user experience you're shipping?

There are popular, free screen readers out there and using one can teach you a lot.