Search:

On the scale of a razor bevel the changes would surely be so miniscule that it would be next to impossible to guage by hand particularly if there were a rotation of multiple razors in question which...

That is something I don't remember hearing before.

This is where an X or wiper stroke comes in, particularly on smiling blades.
As has been said, it really is a question of practice. Take it slowly at first and watch what is happening then you...