As for sharpening, see Lee’s book on sharpening. Also, Mike  Wenzloff writes
this:
Due to the shape of what would be called the bevel, they are easiest to sharpen
either with the side of a grinding wheel (light pressure) or by using a stone
set near the edge of the bench and the chisel's "bevel" oriented so the handle
is over the edge.

A swan neck chisel (or, lock mortise chisel) doesn't need a high degree of
sharpness. It is a scraping tool designed for cleaning out bottoms of mortises.
I usually leave it as is off the grinder.

Cheers
John

“P.S. If you do not receive this, of course it must have been miscarried;
therefore I beg you to write and let me know.” - Sir Boyle Roche, M.P.