Here we assume that
the cutting edge geometry is actually correct,
no jags are visible,
but the iron has just become blunt through use, and
now to be restored to a sharp condition.
the bevel also does not need to be renewed:
any micro bevel is still short enough
a worn bevel does not yet need to be straightened again
If this is not so: first repair the bevel.
If, on the other hand, the edge is just a very tiny bit dull, you might try using a honing leather to see if you can get there.
If that doesn't work either, we'll keep going: They reach for something like 1000 grit.
Then the problem arises of setting the correct angle:
if the iron is to be ground by machine, it is advisable to test very carefully first whether the setting is correct. It is better to first turn the disc by hand and see if the grinding marks are in the right place.
if you want to proceed manually with grinding aid, clamp the iron for the desired angle, and
if you prefer pure hand grinding, feel the tipping points of your iron.
And then work your way up to the desired finest grit (normal is factor 2 to 3 per step). Some are satisfied with grit 5000, others enthusiastically go up to 10000 or even higher. Do not overdo it! It is important that you always use the finer grit to erase the traces of the coarser grit. This is not easy to see. Take your cue from the gloss.
One possibility: They manage to work with any grit
to produce a continuous burr (the burr, however, becomes less and less noticeable with the grit), and
with the same grit afterwards to remove the burr again without spoiling the cutting edge.
Afterwards, it is still recommended to use a stropping leather.