That's a good photo.
A fine diamond stone is useful as the surface will stay flat.
I would suggest that the top of the c/b is supported on a small prop (stick of wood) which is 3mm lower than the surface of the stone.
This gives an undercut of approximately one and a half degree.!
A nice pilot who spent time here taught me the one in sixty rule, 1:60 is about one degree!
Black felt tip or Sharpie is good for monitoring progress.
happy new year,