....
If you're familiar with draw filing, that's the way to remove dings on a
table. A single cut file (best not a new one, which is usually quite
aggressive) is placed on the table of the mill and drawn sort of sideways
along the table with light palm pressure on the file. Given the proper
application, it glides over the table with no consequence, but removes
anything that stands above the table. Cast iron is very good about
cutting
away easily, unlike steel. If the file traverses the surface smoothly
and
doesn't hang up on anything, the table is clean. If anything stands up,
you'll feel it. Just repeat the process until you don't. You'll be able
to
see where it was, and how it was removed to flush with the balance of the
table.
....

Harold,
I routinely do just this thing. Except, oil the table and use a stone.
Dropping items on the cast surface or clamping steel directly to the table
will raise a very small dimple. The stone removes them nicely.

Karl