Cation about the greyscale thing, converting color to B&W on a computer, making B&W Xeroxes, etc, can never come close to what actual film does. At best, it's just another way to arrive at a guess. The contrast that you get with real film is so much different than with conversion to greyscale on a computer screen, MUCH less contrast with greyscale. Plus, different film stocks, use of filters on the lenses and filters and paper used in making the photo print make for too many variable to be able to account for accurately.
As long as that is kept in mind. There's nothing wrong with checking that way but it's not a safe way to make any definitive decision.
No offense Baron, you're probably aware of this, but not everyone is. It's always good to add a disclaimer to anything when you're interpreting B&W photos
